Ah I remember those days! My first (and only) homebuilt system was a P4 2.6Ghz with a 9800Pro... same system today but the 9800 crapped out back in January so I got an nVidia 6800XT.
For the new computer I gave myself a budget of €1200: even with an OEM copy of Vista Home Premium 64-bit, the full system box came in around €1180, but bear in mind that's without keyboard, mouse, monitor, or dedicated sound card.
For €1300 I'd recommend building a high-end system around a Core 2 Duo processor... the quadcore chips will continue to be under-utilised by most programs and games for at least another year, by which time the other hardware components will have evolved anyway. The next batch of AMD chips are still a fair bit down the road, too early to evaluate.
Motherboard choice depends on your needs, but for instance I chose the Gigabyte board because it is a good overclocker without SLi (pure marketing ploy as far as I'm concerned) and without too many bells and whistles, so it was significantly cheaper than other Intel C2D boards.
Graphics card... try and resist the temptation to blow your budget on 2x8800 Ultras in SLi!!! There's absolutely no point blowing 200/300% extra for a 15/20% performance increase, especially when it's the difference between 130FPS and 160FPS. By seating an 8800Gts in a good system and tweaking a little, you'll still get blazing gaming performance at medium resolutions (up to 1600x1200 or thereabouts, which is still pretty damn high to me). Sure, a year down the road, the headroom that the more expensive cards provide will begin to show, but by that stage their prices will have halved, and the 8800Gts will still be performing strongly even in DX10 applications. Put it this way: when Storm of War comes out, you should have a system that's more than capable of playing it at max settings. Just be sure and have a big juicy power supply. The Corsair 520W should be enough, but I opted for the 620W as I'll be overclocking other components in the system and will need the increased voltage.
As regards RAM etc., the following thread was pretty much the deciding factor in my choice of setup:
http://forums.overclockers.co.uk/showth ... t=17636047" onclick="window.open(this.href);return false;
I put 2Gb in for Vista compatibility, but once I have a few more yo-yos I'll strongly consider an additional 2Gb.
The Antec 900 is a big-assed case but features incredible cooling as-is, and, very importantly, provides room for the (massive) 8800 card!... I'm not concerned with the visual appearance of the computer but this case does look pretty cool and stealthy
But of course, all said, I'm yet to get the thing up and running... I'm still awaiting delivery of the 8800, the PSU, DVD+RW and mobo. I thought it might have arrived today when the case was delivered (ordered at the same time) but for some reason they ain't here yet. Assuming the thing doesn't blow up at first boot, I'll let you know how the thing behaves, and how it handles games, ASAP.
Good hunting!