AGP 2x/4x v. 4x/8x

[NSchandler]

I'm looking to buy a new videocard for 2 primary reasons:
1. I want to purchase a 2nd 2001FP when they go on sale
2. My brother wants to play Battlefield 2 with me

I have integrated video right now (blah), but I read that you can still install a video card in your AGP slot (I verified that I have one).

When I search for AGP cards, however, it lists 2x/4x cards and 4x/8x cards. How do I know whether my AGP slot can support 4x/8x cards?

On a slightly different note, if all I want to do is run 2 2001FP's and play Battlefield 2, what specs do I need to look for in a card (other than 2 DVI inputs)? Any suggestions for particular cards?

Thanks.