Sometimes size isn't all that matters.

Financial Planning's FP50 rankings list IBDs based on total revenue. Yet as part of the data collection process, we track a variety of other performance statistics -- overall payout growth, high-value accounts, high-end reps and more.

Often, the standouts in these other categories do not generate enough total revenue to make the FP50 rankings -- but their outperformance makes them worth watching.

Check out four independent IBDs that you may not know -- but probably should.

1. Summit Brokerage Securities

Summit Brokerage Securities in Boca Raton, Fla., lands in the No. 64 spot in the overall rankings -- but among the respondents in the FP50, it has the most advisors with production above $150,000 -- a whopping 93%.

"If we wanted to be in the top 50 we could be there anytime we want," says Marshall Leeds, president of Summit. The firm, which is home to 345 advisors, turns down roughly 80% of those who attempt to join the firm, claims Leeds, who explains that the exclusivity is what makes this firm different.

"We are a firm that is built to go after high-producing, quality advisors," he says. "We take quality over quantity."

Summit generally hires advisors with 15 years of experience in the financial industry and arms them with everything from training sessions to the cell phone numbers of all executive members of the firm. "Half the advisors do not use our practice management," he says. "The other half do, and that helps them grow their business."

There's another advantage to working with experienced advisors, Leeds says: fewer compliance headaches.

Meanwhile, Summit's performance has not gone unnoticed: RCS Capital snapped up the IBD in a deal that closed this June.

2. Prospera Financial Services

Prospera Financial Services, in Dallas, credits a similarly focused strategy for its own success.

With revenues surging 45.8% in 2013, Prospera comes in second on the list of fastest-growing IBDs. The firm, which has roughly 250 advisors, ranks 67th on this year's FP50 list overall.

"The biggest reason why we're successful is that we're not striving to be on the top 50 list," says Tarah Carlow, SVP of marketing and engagement at Prospera. "We have our niche and we want to be the gold standard for boutique firm."

Carlow argues that the firm's emphasis on practice management and entrepreneurial spirit is what's boosting average production numbers.

"We're looking for people who are qualified to be business owners," she says, adding that the firm wants advisors who are headed somewhere specific -- not running away from something. "Not everyone is fit to be independent," she adds.

3. Sammons Securities

Based in Ann Arbor, Mich., Sammons Securities turns up just a few slots lower on the list of fastest-growing firms, at No. 5 -- with revenue that surged 28.5% last year -- while in the 65th spot on the overall rankings.

Once again, targeted recruiting seems to be key. "We try to control growth so we still know all the advisors personally," says Tony Bacarella, executive management and a registered principal at Sammons Securities.

"We have the same products and great technology as other firms," says Bacarella. "But what separates us from other firms is that we really know the reps personally. We have a very low turnover rate."

The closeness of the firm culture boosts production and creates a better quality of life for advisors, Bacarella argues.

4. Harbour Investments

Looking for IBDs with wealthier clients? Harbour Investments in Madison, Wis., has the third-highest percentage of accounts with more than $100,000, with 57% of accounts over that benchmark; it sits at No. 68 on the FP50 list.

Regional connections and hands-on training get some of the credit, says David Rosenow, Harbour's vice president for business and product development.

Advisors are chosen based on proximity, he says, and executives drive to visit reps four to five times a year. "We view this as a partnership," he says. "We treat them the way they treat their customers."

The firm trains and encourages advisors to "get access or control of all client's assets" and "not do a piecemeal thing," he says -- an attitude he says accounts for Harbour's percentage of larger accounts. "It is about the relationship," he says -- "not about all the big numbers."

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