This beast of a Hackintosh uses two server-level Intel Xeon E5-2690 processors ($2000 apiece), and includes a whopping 128 GB of RAM. With this setup, lightinhopkin's computer clocks a Geekbench score of approximately 40,000 when running Windows 7. For the sake of comparison, the Intel Core i5-2500K (the preferred choice for high-end Hackintoshes) barely clocks 11,000 on Geekbench on good days.
Incredibly, the SuperMicro X9DAI motherboard ($500) used by this build is almost completely compatible with Mac OS X Lion. According to the build thread, the X9DAI works with a standard Unibeast+Multibeast installation that's virtually hassle-free; almost all of the motherboard features are supported, including audio. The only feature that doesn't work is ethernet, but this can be remedied by using a USB Ethernet Adapter, available from the Apple Store.
Mac Pro is long overdue for an update, and it's likely that new models of the Mac Pro will use these new Xeon processors.
lightinhopkin's build costs over $7000 to assemble, which is far more than most of us can afford. However, it absolutely stomps the Mac Pro in terms of cost to performance; purchasing a Mac Pro with similar specifications would cost almost twice as much. If you're looking to a maximum-performance Hackintosh server, be sure to check out this build. Even if you can't afford the dual Xeon processors and 128 GB of RAM, the comparatively cheap SuperMicro X9DAI motherboard is an enticing option for any Xeon Hackintosh.
SOURCE: 128 GB RAM and 16 Cores / 32 threads X9DAI
UPDATE (July 4, 2012): If you're looking to build a high-end Hackintosh server for yourself, check out this similar Xeon Hackintosh build assembled by Paradigm99, as well. Compared to lightinhopkin's build, Paradigm99's build uses an ASUS Z9PE-D8 WS motherboard ($600) and slightly cheaper Intel Xeon E5-2680 processors ($1700). But importantly, Paradigm99's build actually appears to be optimized for Mac OS X, scoring an incredible 28,000 in Geekbench.