The XFX 7800GT that I linked you to is the best buy on a 7800GT on the market right now. You may find one for like $10 cheaper, but no other card has stock overclocks the way XFX does on the 7800 series cards. Not only that, but I think it's the 2nd cheapest on newegg. Newegg is easier to deal with than tiger, too.
It's up to you, man, but right now the 7800 series cards are the #1 cards out. ATI's x850xt pe is still a killer card, but still a step behind, a big enough step to say that the extra $40 is worth it for the 7800gt.
No matter what decision you make, they are both good deals. It all depends on what you wanna spend.