OK, since I'm here, and asking advice from you lovely, lovely people (and laying it on a bit thick, as is my custom), I thought I'd post my finalised build here in case I've made some horrendous, obvious error that makes people hear a donkey sound in their head. Please let me know if I've done so, preferably by making the donkey sound then explaining exactly why.
Case : Corsair Graphite 600T White
PSU : 800w Coolermaster Modular 80+ Gold
Mobo : Asus P8P67
CPU : Intel Sandy Bridge 2500k
Cooler : Noctua NH-D14
RAM : 8GB Corsair XMS3 1600MHz 9-9-9-24 (1.5v)
OS Drive : 120GB OCZ Vertex 2 SSD
Other HDDs : 1TB Caviar Black
2 x 2TB Caviar Green
Graphics : 2x Sapphire HD6850 Crossfire (I already have one)
OS : Windows 7 Home Premium 64-Bit
Optical : Samsung Lightscribe DVD Burner
Sound : Creative Labs Sound Blaster X-Fi Extreme Audio PCI Sound Card
Wireless : Edimax EW-7612PIn 300Mbps Wireless 802.11 b/g/n PCI Express
So if there's any obvious bottleneck or possible incompatibility, please let me know. I think this is a pretty good build but it is my first one, so please be brutal. It's the only way I'll learn.
Thanks guys.