Updated from 1 p.m. EDT

Financial stocks slumped again Wednesday to mirror the movements of the broader market, but big winners emerged in online brokers TD Ameritrade ( AMTD) and E*Trade ( ETFC).

Ameritrade climbed 3.8% in furious trading after announcing that Jana Partners and SAC Capital Advisors, which have disclosed owning around 8.4% of the company with the intention of acquiring additional shares worth more than $600 million, want Ameritrade immediately to pursue a merger with another broker. The firms specifically named E*Trade and Charles Schwab ( SCHW) as possibilities.

The firms also stressed that they wish to avoid "interference" by 40% shareholder Toronto-Dominion Bank ( TD), which they say "may be standing in the way" of such a merger.

Ameritrade gained 76 cents to $20.71, and E*Trade traded heavily to jump 7.3% at $25.60. Charles Schwab lost 1.1%, and Toronto-Dominion -- a member of the NYSE Financial Sector Index -- gave up 0.7%. The index sank 0.9%, or 84.93 points, to 9825.97.

But another component of the index, subprime-mortgage lender NovaStar Financial ( NFI), continued rising today following Tuesday's announcement that the Kansas City, Mo., firm had securitized $1.4 billion in nonconforming mortgage assets. Shares bounced 11% to $9.10.

The KBW Bank Index, which tracks large banks, fell 0.9% to 115.36.

As for individual names on the losing side, United Fire & Casualty ( UFCS) slid 3.1% to $37.71 after A.G. Edwards cut the Iowa-based insurer to hold from buy, and Prudential Financial ( PRU) shed 1.1% to $99.46 on word the New Jersey life insurer is shutting down its equity-research business, Prudential Equity Group.

Elsewhere, shares of Hilb Rogal & Hobbs ( HRH) slouched after the Virginia-based insurance broker agreed to buy Charlton Manley, a Kansas-based company that mainly operates as an insurance agency. Hilb Rogal was off 11 cents to $43.71.