Ati products do not have any distinct advantages over nvidia products in an HP case (nor any other distributors for that matter). Hp decision to ship ATI products came about from a cost driven standpoint. The X1, hd2, and hd3 series are successors in order from right to left (3 being greater than 2 ect). In each series there are the high end ( x8xx- x9xx ) middle ( x6xx) and lower end cards (x1xx - x5xx). Generally the high end of a series is a bit greater than the middle of the next series .An x1900 will offer better performance than an x2600. However, to further confuse you, because technical specifications will do that, the x3000 series is really the x2000 series rebadged. There was no *real* technological jump.
As for a card suggestion, I suggest you go with this card
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121237
It has 512mb of good memory, and will run the latest games on medium without too much of a problem. The 3850 is a little out of your pricerange, but would be the next step up (at 120 after a rebate).
As for a card suggestion, I suggest you go with this card
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121237
It has 512mb of good memory, and will run the latest games on medium without too much of a problem. The 3850 is a little out of your pricerange, but would be the next step up (at 120 after a rebate).