Technically you could get a pc like this for half it's price except I'm not sure how they connecter 4 video cards and made them work.
Last week I built 2 pc's for my friends. One based on newest AMD's Phenom and another on Intel Quad Core QX6700 -those beat any other cpu's Mac could use including those 8-16core xeons if it comes to media performance, intel's processor is also much faster if it comes to compressing and stull like that. They simply have much better performance.
second (more expensive) PC had 8gb (can upgrade to 16gig anytime) Geil 1333mhz ddr3 ram so that's nearly 2 times faster than rams used by Mac and a single geforce 8800gtx by EVGA - there's still no use to put 2 of those cards in SLI.
I also found cheap 24' full HD Dell monitors (700-800$).
Friends study in school which provides them with all Microsoft software licences for free so no software was needed.
Less expensive pc (with 8gig of 800mhz ddr2 ram and a single 8800gt) costs around 1500$ while the more expensive around 4200$ + 700-800$ for monitors.
So it's 2200$/5000$.
Both have newest, good Asus motherboards, WD or Samsung dual 500gb drives in Raid so they're 2 times faster and Chieftec/Tagan 620W power to prevent any possible resets and troubles.
Bare in mind that electronics here are much more expensive. For example a simple 19' monitor on a S-pva matrix is more than 2 times more expensive, processors, graphic cards are nearly 2 times more expensive than american ebay prices.
I managed to find cheapest suppliers.