Building a SmallForm Factor... Help!

[cuserounder]

OK, I'm putting together a SmallForm Factor barebone as a Christmas present from my parents.. I'm aiming for $400-$500, but if it costs more, I can throw in some of my money or gift money from others...

I already have a 17" flat panel monitor, wireless mouse/keyboard, speakers, all that sorta stuff... Here's what I need the computer to handle:

6-8 tables, PokerTracker, GameTime+, Firefox, ITunes/Media Player, AIM, [censored]/[censored] all open at once..

At other times I'll be using audio editing software - but my guess is if it can handle my crazy multi-tabling/multi-tasking, it should be fine for audio editing.

Suggestions on whether to go with AMD or Intel and what speed and how much RAM are greatly appreciated. I'm looking at a Shuttle barebone smallform factor...

I asked a friend (who doesn't play poker so isn't familiar w/ multitabling and all) what he thought I'd need to have 10-15 applications running at once.. He suggested:

AMD Athlon 64 3700+ 2.2GHz

2x1GB DDR RAM

Western Digital 320GB 7200RPM hard drive

Shuttle XPC SN21G5 AMD Socket 939 AMD Athlon 64 /Athlon 64 FX /Athlon 64 X2 NVIDIA GeForce 6100 Barebone

That comes to about $600.. Where can I cut back? Where do I need more? Anyone have any experience they can share with this type of a set up?