#1 There's no real point getting an extreme processor unless you're overclocking.. well not really... and if you burnt it out could you replace it?
#2 In terms of graphics cards you'd best have a good long hard look into reviews as the Nvidia offerings seem to be a little stale now, to me anyway. Each new model is pretty much the same as the previous one. Personally I backed ATi this time and the 3870x2 which I got works well... perhaps not so many screaming frames per second but each one seems to look more polished than the Nvidia versions..
#3 Raptors are okay if you have money to burn but the present terabyte offerings are pretty damn quick and far more cost effective.. as for RAID I think Anandtech reviewed it and found little performance gain for a desktop. The main thing is to put your games on a different harddrive. Perhaps one raptor and one TB drive? Oh and keep your eyes open for the Velociraptor. Larger (320GB) and 30% quicker than a raptor 150GB.
#4 Memory. If you go for DDR3 then spend a LOT of money otherwise it's just a label. DDR2 however, you can get decent speed for less cash these days.
Oh and have a look at the elite stuff on
Homepage | Custom PC They're usually pretty good if a little behind the bleeding edge. Xtreme Systems forum may also be a good place to ask around. They have systems that would make Bill Gates weep for joy!! Think liquid nitrogen cooling geeks and you're pretty close
Oh and for an OS, Vista IS faster... there's no doubt there but it's buggy. XP is fine but 64 bit is my choice of preference and I very rarely have any compatibility problems... what I do find is that I end up with a less bloated system after six months as most bloat ware tends to target the 32bit suckers... errm I mean customers
Edit :-
You're getting a monitor too? Well I just bought the HP 24" widescreen and it's dreamy. Sure it's a TN panel but with the price of the "proper" panels being a whole hell of a lot more money.. I don't care.
Sound card wise, I'd caution against XFi cards, they tend to cause problems. I'd reckon your best bet is to find yourself an audiophile site and get a cheap card (they pay hundreds for theirs so cheap is not necessarily cheap if you catch my drift). If you want a gamer card then check out Razors card. It's pricey (more than an XFi 64Mb!!!) but I'm hoping they don't have as many bugs as the XFis (Creative are terrible for drivers... just ask the Linux XFi crowd).
Case wise (an oft overlooked part) if you don't mind noise and want to stick with air cooling then get the Antec 900. Nothing else competes for the price... not even close. If it's watercooling that's wetting your appetite then good luck.. that little quandary took me several months until I gave up and bought the Thermaltake Mozart as a "screw this I'm getting the biggest f'in case on the market!!!".