"Turnover in the service provider space has been significant since the new fee disclosure rules took place in 2012," said Schweiss, who explained that much of the organic growth in 401(k) business has come from RIAs who have existing relationships company principals and executives in their personal wealth management books of business.

The potential "commoditization" of 401(k) plans that some feared would be the result of stricter fee disclosure rules has not happened, said Schweiss.

Neither will a new fiduciary rule that looks anything like what the Department of Labor has proposed end up homogenizing the industry, said Schweiss.

"There will always be room for differentiation between retirement providers. That variance in the products and services has given us the opportunity to grow," he said.

Like a lot of stakeholders, Schweiss is reluctant to predict outcomes over where the rule goes from here. TD Ameritrade does not have its own proprietary mutual funds, so he doesn't fear new conflict of interest rules that would address provider self-dealing.

Nor is he sensing any great consternation in TD Ameritrade's RIA channel over the prospect of a new rule.

"We're not seeing advisers getting very worked up over there this. Fiduciary RIAs shouldn't be affected at all. And even in the broker-dealer community, we are starting to see leaders come out and say they are more amendable to the DOL's ideas," said Schweiss, referring to public comments made by the heads of Merrill Lynch and LPL that strike a more accommodative tone than the DOL's more assiduous opponents.

While he doesn't see an organized voice from plan sponsors, small or large, that could move then needle in the argument, common sense suggests where they would likely weigh in on the wisdom of the DOL's proposed rule.

"Why would a sponsor oppose this? This is clearly a movement in the direction of putting clients interests front and center," he said.

The question of whether or not RIAs in TD Ameritrade's channel, or any other, will be unaffected by a new rule is subject to debate.

In its cost analysis of the rule, the DOL says the numbers of RIAs and broker-dealers have "considerable overlap."

More than 11,000 RIAs are registered with the SEC, and more than 15,000 are registered at the state level. About 5 percent of the SEC-registered RIA firms are also registered broker-dealers, and 88 percent of all RIA reps are also registered broker-dealer reps.

Mike Welker, president of The Bogdahn Group, a defined contribution and defined benefit specialist RIA firm with over $59 billion in assets under advisement, says the Florida-based firm is "100 percent fee based."

"No one is licensed to receive a commission in our firm," a distinction from the "vast majority" of RIAs who are receiving commission compensation, he said.

Bogdahn for one would lobby for a stronger rule than the DOL proposed, which of course does not prohibit advisers to 401(k) plans from receiving commission income or 12b-1 fees.

"No one should get paid on what they put in portfolios," argues Welker. "Advisers should be compensated on the competency of their advice."

The amount of hidden fees buried in the investment management world is "virtually impossible to quantify," he said.

"There are costs borne into the system getting leaked out, and ultimately that weighs on the performance of participants' assets. As advisers to plans, we can't control markets, but we can control the cost of advice, and the quality of it."

What may be most frustrating to Welker is the frequency with which he finds sponsors and institutional clients are in the dark when it comes to the layers fees that he says amounts to hidden costs.

"What we want to see is full transparency. We want our clients to understand the full extent of who is getting paid on their assets. Then they can make decisions that are in their best interests.

Ultimately, Welker is extremely confident new conflict of interest regulations will be good for investors and good for sponsors. "That's where the conversation should start and stop," he said.

David Marotta should be jumping for joy after the release of last week's DOL proposal.

His smaller Virginia-based RIA firm oversees $280 million in assets, and has a growing presence the 401(k) space, largely because his group is able to keep plan costs, even for smaller plans, around 70 basis points of assets, he said.

His firm's compensation is strictly fee-based.

"I don't think the DOL rule will be helpful. The fiduciary standard is a principal; it is not a rules-based standard. The DOL is trying to change that. I fear what we're going to get is a huge new set of rules that will amount to a suitability standard warmed over," he said.

Already, Marotta says he personally spends "hundreds of hours" complying with SEC regulations.

"That brings nothing to my clients," he said. "I don't think new regulations make investors any safer."