Mine is a personally built desktop that has the power to rival Alienware systems available at nearly twice the price I paid for the individual components.
AMD Phenom II X6 3.4 Ghz (not overclocked, haven't had any reason to)
dual Geforce 550 ti cards (2 GB each)
16 GB RAM
100 GB SSD for the windows install
dual 500 GB HDDs in a RAID 0 format for other applications.
As for the model, I suppose I'd go with the Nissan Maxima
Not incredibly impressive to look at, particularly when compared to the lamborghinis popping up, but packs a surprising amount of performance in.