Anyway, let's get something straight man. It is not wise to buy from a company generally. Dell overprices things... and that is how they make their money. Seems logical to buy a computer because the know what they're doing, however, the overcharge a ton. Out of curiosity I made a virtual Dell online one day just to see how it stacks up to the real price. I managed to build a $4000 Dell for just over $2000. You're paying for them to build it pretty much.
If you already have Windows XP and whatnot from an old computer, building your own pc would be the best idea. You could have a pretty happenin pc for that same $1200 you're going to spend on Dell.
And for the record, the Radeon X850 is not really as good as the 6800GT. Look at other threads by doing a tech-forum search. You'll see that NVIDIA pretty much owned up on this series of graphics cards.