I have a very specific program that I need to have running as fast as possible. I wish to buy a super-fast PC in order to run it. The program is already written to make use of multiple cores and on an N-core machine it will run very nearly N times faster. The program spends almost all of its time performing integer operations with no disk access and very little IO so I don't care about graphics or hard disk performance at all.
I'm nervous of things like liquid cooling and overclocking and suspect that the little extra speed you get from that is rather poor bang for your buck (feel free to persuade me otherwise). From my limited knowledge so far, I suspect that the best I can do is find some motherboard that can take two Intel Quad core processors? - though I've no idea who makes them.
I've noticed that very often, when trying to by unusually fast PC's, the price per unit of processing power starts to grow almost exponentially above a certain level... So I guess I'm after something that's as fast as possible without becoming very poor value for money.
EDIT: The program is my own (and so can be modified if necessary). It uses multiple threads. It runs on windows. I do have a text-interface linux version, but that's very much a last resort. My budget is up to around the ballpark of $2500.