choosing an investment management firm

[tannenj]

so, i'm looking to start investing poker money and am trying to wrap my brain around some of the strategies discussed in this thread. i'm planning to deposit $20k or $25k in a month or so and then supplement it with $5k-$10k every month or two thereafter.

my question is simple: which company? i've seen vanguard mentioned. my dad suggested t. rowe price and one or two others that i'm having trouble remembering right now. i know nothing about any of these companies. what's the difference, and how should i decide?

thanks.