If you’re sure that all the software you’ll be using is 64 bit (or will work under 64 bit) and that all the hardware in and around your computer has 64 bit drivers, then go ahead and install W7 64 bit.
Lots of things (hard and soft) are still not 64 bit though, so if I were you I’d do a ‘head count’ - see just how much of your stuff is “64 bit ready” - and if you find that the majority is still 32 bit, install the 32 bit version.
Also, do you have enough RAM to really need, or make use of, the 64 bit version?
Oh - and some things just plain don’t work under 64 bit - like ReWire.
My new system:
CORE i7 2600K 3.40GHZ 8MB CACHE 1155
ASUS P8P67 SOCKET 1155 DUAL CHANNEL DDR3
CORSAIR HYDRO SERIES H50 REV 2
2x WESTERN DIGITAL FAEX 1TB SATA III 64MB CACHE (WD1002FAEX)
2x WD 500 SATA II
EVGA GTS450 1GB GDDR5 - 1450
8GB GSKILL DDR3 12800 RIPJAW X (9-9-9-24) (2x4GB)
I don’t remember the power, cause I’ve to change my old one from Be Quiet 700w. But I’ll post it later with some feedback using it with Cubase 6…