I have a Shuttle SD37P2 which places like
http://www.overclockers.co.uk/ sell, I got mine from Ebay, swapped the 2GB RAM for 4 and put a Quadro graphics card in as I am a CAD nut, but CAD and gaming are very similar apart from the card (which is the same Quadro/Verto but with different firmware) I paid all in all about £500, it also has 800GB storage but I have lots of movies, if your thinking of building a PC from old bits I would go against it as if the bits are over about a year old, something quicker will be out and your old bits will be the bottleneck, making the whole system slower and wasting the new fast componants you have and thus your money. I like shuttles as they are quiet, they are also good for system componant life as everything runs cooler, think of it as putting all your parts in an aluminium tube with vents in the side and a fan at the back, cool air goes over everything and thus things last longer, the also take up less room which leavs more room and money for 24" monitors which are now £250 with DVI input, judging by the spec somebody knows a bit about PC`s, if you found an online PSU calculator
http://www.journeysystems.com/?powercalc you will see that most systems dont need the PSU`s people put in them, indeed I rape my machine doing complex stress analysis and aerodynamic calcs and my piddly PSU which is about 500W never fails, I also assume that the mobo chosen already has a decent sound card on it and would he notice the difference between that and the card he askes for?
Personally I always by my PC gear when it is a few months old so I am not paying for top notch stuff at silly prices (the same way some people never buy new cars,) so the `more power than a kray` CPU would be nice but I dont think neccessary, something slightly less powerfull will be a lot less money, also I think gamers take as much pride in their rig as they do their gaming skills, so some of this is the young man being able to gloat about the power of his system....
