The Geforce 6800 GT is a very nice card; I'm using it for the system I'm building now. However, it hasn't been benchmarked with HL2 yet...so if you're thinking of purchasing that, you might want to wait until it’s released.
However, like dreamliner said, it's pretty hard to get the latest hardware and expect it to be the best in 6 months time. Best bet would be to budget, and then just go for it
yeah def mate i was waiting for ages then i just went for it and bought some Corsair TWINX 1024-3200XLPRO, Athlon 3800+ and an av8 deluxe mobo and i'm loving it even with my crappy 9600 graphics card untill i get my gt in a week or so
I'll try to help you - do you have any machine now? (If so give spec. so we know where we start/ have to improve / could work from)
Do you have a budget? Care to share it? (Then we could say what you might get if you built now)
Are you building from scratch? (Presume so, would have an idea from above answers)
But still behind this there are a number of things that can be said - you could make a bargain gaming machine and do it right away IMHO but do not expect the most screaming fast machine, although with careful build selection and over clocking you can achieve remarkable value. For this you'll need to avoid any 64 bit or PCI Express, any extras you are spending on are going to be decent memory and the graphics card, and maybe a faster HD I guess.
I would go for it now if this fits the picture of what you want - but if you are thinking you want PCIX and 64 bit then just hold your horses - because we do not even have the OS or drivers or graphics cards out there yet and you will pay a huge markup for these products which are only just coming through in volume...
Just my thoughts from what I know, I only play the odd UT2004 I am no real gamer....