If you ask me, I say forgo the 975 all together. Buy a 920 and use the easy overclock utility on either of those boards to over clock it. For what you sound like you're doing, you don't need the computing power of the 975 one bit. Don't forget, we are dabling in the Ultra-high end CPU market and anything you buy with an 'i' in the name is going to more power than you need.
To help you out, here is what I suggest.
If you are just really power hungry, go for the i7 920 and just be patient for the Westmere/Core i9 line to come out in a few months(6 cores), then put your money in that. I say purchage the Rampage Extreme and a cooler that will give you no reason to worry. (Prolimatech Megahalems w/ a couple of Coollink WiF2 fans)
http://www.heatsinkfactory.com/prolimatech-megahalems-cpu-cooler.html
Use a good thermal paste (IC Diamond 7/24 Carat TIM, don't be fooled by the very old Actic Silver stuff)
I say spend your money on a fantastic storage device. SSD or HDD is a tough decision to make. Personally, unless you are using a program that requires a rediculous read/write speed, forget the SSD and get yourself a VelociRaptor that will perform. If budget is an issuse (which apparently it isn't with the 975), then buy yourself a Seagate Barracuda 7200.12. THe .12 is very important, they have many different revisions of the Barracuda series, that is the latest and fastest, and even benches up there with the VelociRaptors.
The biggest thing to do, is to not OVERGEAR your PC for your current needs, this will save you hundreds of dollars and you'll never know the difference. If you need some more help chosing just post in this thread and i'll be watching. GOOD LUCK!