that depend on what you intend to use a computer for. is it gaming, writing, rendering, and so on. as you see there's different fields, and each field require a specfic computer. but if you just need a monster good computer i guess you'll only need to pick the most expensiest hardware you can find.
Not sure what you consider to be the "best pc", but i would post on those tech forums where they can give you a quote... depends whether you want to buy a packaged PC or build it yourself...
^ with that aside, BUILD A SUPER COMPUTER DOOMSDAY DEVICE BUY PURCHASING THE BEST PARTS OUT THERE AND ASSEMBLE IT YOURSELF!! it will be obsolete in less then a year.
go alienware and purchase all of the most expensive selection and get one of those dell 30" ultrashard screens, one doomsday machine coming up
the old thread reviver, theres only one person i have in mind. and im sure you're not the guy whos revived 6 pages of old threads now are ye?