I'm puzzled you went with and AMD64x2 instead of core2duo, since money doesn't seem to have been your biggest concern; around here, I could have gotten a E6550 for the same price as the 6000+. But oh well, it's going to be a decent enough machine anyway.
GeForce 7600 is a pretty decent card, relatively fast but not one of the monster power consumers. I'm fond of my fanless one, and I certainly like the NV drivers a lot more than the buggy stuff from ATI
If i ever want to go for something better, i guess i'll get another SLI card (that explains why i went for a nVidia card).
You do need the second card to be exactly the same as the first card, though, don't you? Might be difficult finding that once you get to the point where you need the extra performance. Of course you can always get a new (or two new
) cards then, but then it defeats the "economic" aspect of SLI.
I do run a SLI motherboard myself, but that's only because it was the only fanless motherboard available at the time that was also stable.
4gb shouldn't a problem under XP, not under the 32bit version either, you just won't be able to have a single app use all the memory.