I've got a hackintosh: i7 3930K (6-core), GTX 680, 32GB RAM, 27-Inch Apple Cinema Display. Geekbench is about 22000. Built a few years ago for about $3000 all up (ram was a lot cheaper back then). It's been a brilliant machine ever since, completely dominating the old Mac Pro and still topping the equivalently priced newer model in every respect except SSD speed. Looks beautiful on my desk too.
It took a lot of care and effort to get this machine working at the same level of perfection as a real mac though, lots of things to learn about, fix and tweak (audio, sleep, power management, imessages, full-screen boot etc.) But man once you get there, you truly do have the best of both worlds.
BUT... in this case I would have actually bought the iMac. You really can't go past that display, an equlivient PC and display would actually set you back slightly more if you bought your ram separately.
Bottom line is this: sometimes Apple prices their computers really well (this iMac for example), other times not so much (most Mac Pro configurations). I always go Apple for laptops, but for powerful desktop rendering machines, I'd usually tempted to go hackintosh.
But seriously, if even one of these things doesn't apply to you...
1. You're a bit of a tech head and have the experience to pull this off.
2. You enjoy customising, upgrading, and tweaking.
3. You're willing to put in a lot of your own free time.
4. You NEED bang for your buck, big time.
... just get the mac!