newb question about graphics cards

Around Christmas I got a new PC pretty bad a**, quad core, 3 gigs of ram, 500 Gigs of Disk Space, and I have a ATI HD2600Pro 512 MB GPU.

My two questions are....

1. Is this a decent card for the next few years, I play GeOW well enough, and Bioshock but I get the feeling I'm not getting enough out of my games

2. OK this is my seriously newb question....is it ok to go from an ATI card to a Nvidia card?

1. it is a decent card for entrance gaming, its not to powerful but also pretty cheep.

2. yes

It's an ok card (although I don't know why you got the 512MB version), but it isn't ideal. Considering your systems specifications, upgrading to a more powerful card like an 8800GT would help a lot. If you don't mind turning down a few settings then you don't necessarily need to upgrade, but it wouldn't be a bad idea to sell your 2600Pro and buy something like this. A cheaper alternative would be the ATI Radeon 3850 or the new 9600GT (Newegg is offering a $10 promo code right now, so better act quick).
BlueBirdTS

Why bother getting an HD3850 when the HD3870 is $185 now? However the 9600GT performed around the HD3870 and beat it in tests but the HD3870 won some tests as well. So its a mixed bag. I would get the 9600GT superclocked for $200 but you can save $15 by getting the HD3870.

Heres the HD3870:

http://www.newegg.com/Product/Product.aspx?Item=N82E16814102719