Thought I'd update on my latest travails.
I found a Gigabyte mobo, a GA-EP45-UD3R, for use with my C2D 6400, but now can't find the CPU. I swear I need to see a doctor over my memory lapses. I thought I put it in the box it came in, but there's nothing but the heatsink in there.
But I decided to test the 9600GSO anyway, and as expected it worked like a charm on my i7-930/Evga FTW3 mobo, and I was able to install Snow Leopard. I've forgotten, though, whatever has to be done so I won't have to keep using the iBoot disc. It's somewhere in here or a linked site, so I'll find and read it again and hopefully get it going. I noticed SL only thinks the system has ~4 GB, oddly.
Another problem I think I'll end up having, though, is that I can't see the hard disk that OS X is on (how does one say that, BTW? I assumed it was OS "ten" since it was the next one after 9.x, but don't recall having ever heard it uttered, and the X is a change from the previous Indian/"Arab" enumerations, so...) from Windows, so I can't format its other partitions for use under Windows as originally intended (I have 4 drives in my case already, and that's the limit, so I got the 2 TB drive to get rid of a couple of the smaller ones). Maybe I can do it using an Ubuntu disc, though.
Anyway, thanks for the help and info everyone has put in this thread. It's very useful for people like me who have no familiarity with Apple machines.
(Edited to correct motherboard's model number.)