Several things that should be considered before buying right now
1. There is a shift about to take place in chipset technology. The first part of that is the P35 chipset which was released in late May, the follow up is the X38 chipset due out next month.
2. Taking that leaps further all of the players are going to be introducing their new chipset motherboards right around October/November. If AMD gets their new one out, there may be reason to switch from Nvidia to ATI because the new R6xx due out in September (and even the 2900XT) will then have the 'mate' AMD designed for that card, essentially opening up the communication path directly to the CPU cores from the GPU. AMD has already broken the 1.5tf real-time dataflow barrier with that chipset, the Barcelona and the next R6xxx card.
In one demonstration, ATI showed 1.5 teraflops of runtime computing ability for a live demo with a lot of demanding 3D effects. It was part of a game which will be coming out before too long and showed a stunning 3D flight through a forest, over some water, past a bird in flight, through the grass and much more. Another demo showed a single machine doing gaming and real-time MPEG encoding on the frame-by-frame generated images for the game. That information was transmitted across a network to be shown on two other computers. It worked so smoothly on the single machine that it almost could not be understood what was taking place. But, according to AMD, it was doing 100% real-time encoding of the images while generating them. The presenter made a point of indicating just how compute intensive this was.
How/if that gets to market this coming xmas season is an unknown but the R700 due out in Feb-Mar of next year will be their next leap and will also need that chipset platform to perform.
The reason the 2900XT did not fair as well as it should have was a combination of things, but the main reason is because the 2nd half of the equation that makes that card light up like a rocket is not on the market. It was originally expected to be out in June/July with Barcelona but got pushed to the end of the year. So the card got a bad rap unfortunately, but as no fault of its own. It had to be released, there was no choice.
3. DDR3 technology is growing fast. They already hit DDR3 2000 and its expected to hit DDR3 2500 by the end of the year, something DDR2 will never do. Also, the new Intel processors due out about November will need DDR3 and the newer chipset motherboards to have full support for them. They will run on the older motherboards but you must have a P35, X38 or next release chipset motherboard for full support.
Where am I going with all this?
Simple, if you are going to spend a chunk of change on a system you may want to pocket that change for a few more months, or at the very least wait for the x38 chipset due out later next month. That way your money will go toward a system that will be completely compatible with the next gen of hardware and if AMD manages to get their next chipset out, that would bust a video barrier long awaited by the game market.
Nvidia from what I understand also has some things up their sleeve too and at this point it is really unknow who will be doing what-when for sure. There is quite a bit of HUSH going on right now so the information about when to expect and what to expect is not clear.
If you want to buy a system TODAY, then a p35 DDR3 motherboard is the way to go. If you wait another month for its big brother, the x38 DDR3 motherboard is the way to go. It will also support full x16 crossfire too, (2 ATI cards in crossfire configuration) something no other motherboard to date supports. The only support 4x-8x crossfire right now.
AS for processors. Here is where you need to decide if you intend to overclock or not. I always do, but that