the new intel 45nm cpu's would be a better choice whether it's a core 2 duo or quad, even the new e5200 dual core which has rave reviews and can be overclocked easily, due to the better performance at a lower power rating. the new 8000 or 7000 series would be a good choice. many local builders are using e5200, e7300/7400, and e8400 for good prices in their pre built systems. however, i'm never really impressed with the mobo choices and definitely would question the psu they would add regardless of wattage.
i recently built my own, giga p45 ds3l mobo, the new intel e7300 core 2 duo 45nm cpu that use less power and less prone to heat up, apline cooling pro 1 heatsink, antec 300 case (comes with two 12 mm fans along with 2 front and 1 side optional fan intakes, coolermaster 500 w psu. i used my old hard drives, old ati gpu card, old phillips dvd flashed into a benq dvd, my old dell monitor and my old 2 x 1 gigs pc-6400 ram.
it cost me almost$400. i could have gotten most of the stuff i already had via bundle deals and such for less than $600 based on what i wanted, less if i chose to downgrade a bit. finding deals is the most important after you research the parts you want and that are compatible with the things you have, other parts, and your needs. i made sure my mobo had at least 3 pci-e slots, i for my uad, and the other 2 for future soundcards or a pci-e firewire card.
the actual building was easier than i thought, with the only issues being attaching the heatsink, because the arctic cooling uses the same method as intels stock heatsinks with the push pin, which feels like you might break the mobo board with the amount of pressure you have to use. the other was attaching the optional fans i bought for it. the screws that come with them are way too small, i goddamn hurt my hand trying to get that shit in the fan cage (thank god antec front intake are detachable) i eventually had to shave the holes to make them bigger but still tight. one thing they never tell you, besides adding more cooling paste if you use a stock heatsink, is that the case needs to have risers for the mobo so it doesn't short out and not to use more than what is actually needed. a little thing that can fry your board or at least cause some serious issues.
i've done a slight overclock to 3 gh fsb 333/1333 and it's running quick and cool. it does more than it's job when making or mixing tracks. i sacrificed taking advantage of uad's wicked christmas/december sale to buy the parts but i'm glad i did
almost forgot, either way, look for xp. i had to get a version from demonoid (xp pro performance edition. wicked and optimized with no bloat) due to my other one being a dell branded oem which would have given some problems with my system i had tried to use it
