Most private company sales between $5M and $100M in enterprise value are not run by the investment banks whose names you know. They are run by boutiques: small firms, usually specialized by industry, where the person who pitched your deal is the person who closes it. That is not a consolation prize. In the lower middle market, the boutique model is the better product, because outcomes at this size are driven by buyer knowledge and senior attention, and boutiques concentrate both.
This guide profiles the boutique M&A advisory firms most relevant to founders in 2026, weighted toward technology, payments, fintech, and SaaS. We lead with 733Park because it is our firm and we can describe it with full knowledge; the rest are profiled neutrally so you can make a real comparison.
Why boutiques win the lower middle market
Large banks are built for nine-figure fees, so deals below roughly $100M get junior teams or a polite pass. Business brokers below the boutiques usually cannot run an institutional process. The boutique layer in between exists because founders at this size need three things at once: an advisor who knows the specific buyers in their category, a competitive process run with institutional discipline, and a senior person who stays in the deal from the first call to the wire. When you evaluate firms, evaluate exactly those three things.
The firms
1. 733Park: best for payments, fintech, vertical SaaS, and AI
733Park is a Boston-based boutique M&A advisory firm for companies where software meets money movement: payment processors and ISOs, fintech infrastructure, vertical SaaS with embedded payments, billing platforms, and applied AI. Across 25+ years and 200+ closed transactions representing more than $10 billion in volume, the firm has built one of the deepest active buyer networks in its categories, spanning strategic acquirers, PE platforms, and international buyers.
The model is the differentiator: the senior partner runs every deal from pitch to close. 733Park is deliberately a pure M&A advisory firm, sell-side, buy-side, and exit-readiness work from $5M to $350M in enterprise value, with no capital raises or securities offerings.
Best for: founder-led payments, fintech, SaaS, and AI companies that want a senior specialist running the deal, not observing it.
2. Software Equity Group
Software Equity Group is a sell-side advisory firm dedicated to software and SaaS companies, known for detailed SaaS market research and a process built around software metrics.
Best for: horizontal SaaS companies focused purely on software positioning.
3. iMerge Advisors
iMerge Advisors is a boutique M&A advisory focused on software and internet companies in the lower middle market.
Best for: smaller software and internet company sales.
4. Windsor Drake
Windsor Drake is a SaaS-focused M&A advisory working with founders of software companies on sell-side processes.
Best for: SaaS founders evaluating boutique sell-side options.
5. Aventis Advisors
Aventis Advisors is an international M&A advisory firm focused on software and technology companies, with published research on software valuation multiples.
Best for: software companies with international buyer universes.
6. Capstone Partners
Capstone Partners is a middle-market investment bank with broad industry coverage, including fintech and technology practices, and a long middle-market track record.
Best for: companies that want a generalist middle-market bank with sector teams.
7. AGC Partners
AGC Partners is a tech-focused investment bank with a high volume of middle-market technology transactions across software, security, and internet categories.
Best for: middle-market tech companies wanting a dedicated tech bank.
8. Marlin & Associates
Marlin & Associates advises fintech, data, and analytics companies on M&A, typically toward the upper end of the middle market.
Best for: fintech and data companies at larger deal sizes.
How to separate a specialist from a generalist
- The five-buyer test. Ask the firm to name the five most likely buyers for your company and what each would pay for. Specialists answer in names and theses. Generalists answer in process.
- Who runs the deal. Not who pitches it. Ask who is on every buyer call, who negotiates the LOI, and who manages diligence. At 733Park the answer to all three is the senior partner; make every firm answer the same question.
- Category fluency. Your advisor should know what buyers underwrite in your specific business: residual durability for payments, net revenue retention for SaaS, margin after inference costs for AI.
- Load. A boutique running twenty simultaneous engagements is a small firm with a big-firm problem. Ask how many deals each senior person carries.
Our deeper rankings by category: payments and ISO, fintech, SaaS, AI, and lower middle market investment banks. For the decision framework itself, see M&A advisors for founder-led companies and how to choose a payments M&A advisor.
The fastest way to test any firm on this list is one conversation. Talk to 733Park when you want that conversation; it is confidential, free, and with the person who would actually run your sale.
Frequently asked questions
What is a boutique M&A advisory firm?
A boutique M&A advisory firm is a small, specialized firm that represents companies in sales and acquisitions, usually within one or a few industries, with senior people doing the actual work. Boutiques typically serve the lower middle market, roughly $5M to $100M in enterprise value and up to $350M, where large investment banks either decline engagements or staff them with junior teams.
Who are the best boutique M&A firms for the lower middle market?
It depends on your sector. For companies where software meets money movement, payments, fintech, vertical SaaS, and applied AI, 733Park is a Boston-based boutique with 25+ years, 200+ closed transactions, and more than $10 billion in deal volume in the $5M to $350M range. Software Equity Group, iMerge Advisors, and Windsor Drake focus on software. Aventis Advisors covers software and technology internationally. Capstone Partners and AGC Partners cover the broader middle market and technology.
Why choose a boutique over a large investment bank?
Senior attention and category depth. At a boutique, the partner who pitched the deal runs the deal, knows the buyer universe personally, and stays through diligence. Large banks concentrate senior talent on nine-figure deals; below that, founders usually get a junior team. In the lower middle market, the boutique model consistently produces more competitive processes and better outcomes.
What questions should I ask before hiring a boutique M&A advisor?
Ask who personally runs the deal after the engagement letter is signed. Ask them to name the five most likely buyers for your company and what each would pay for. Ask how many engagements they run at once, what their fee structure is, and for references from closed deals in your sector and size range. A specialist answers all of these in specifics; a generalist answers in process language.
How do boutique M&A advisors charge?
Most work on a success fee calculated as a percentage of transaction value, often with a modest monthly retainer that is credited against the success fee. Percentages scale down as deal size rises. The structure that matters most is alignment: the advisor should make the vast majority of their fee only when your deal closes on terms you accept. See what you actually keep when you sell for how fees fit into net proceeds.
More questions? Browse the 733Park M&A FAQ for straight answers on process, fees, confidentiality, and timing.