The only thing it does better is handle HD movies.
Go with the x1900xt since it can handle fairly well on its own even now days and has advantages over the integrated with sucking up ram along with every thing else. Just be sure to keep the card clean and run the fan at least 40% then you will be fine.
Agree, stay with X1900 XT, it much better than integrated card. Make sure your card is clean and keep the temps as low as u can, that card's produce a huge amount of heat...