Quick ? regarding the right videocard..

[ARHookEm]

I will soon be ordering a new Dell XPS 420 desktop, when building this system, I am offered three video card options, all of which I will consider. I plan on running a 30' in the middle with a portrait 20' on the right side. My question is which of these will be the right video card to order.
-128MB ATI Radeon HD 2400 PRO
-256MB Radeon ATI HD 2600 XT
- 256MB nVidia GeForce 8600 GTS

I plan on buying this computer pretty much stock, so I am wondering what the correct amount of memory is to buy. All I really do on my comp. is internet, poker, and email.

Is this good as far as a hard drive? Or is this a place I should drop some money?
- 320GB - 7200RPM, SATA 3.0Gb/s, 16MB Cache

-Thanks a bunch guys-

AR