Since your going to run XP64 no over 4GB RAM isn't a waste of money the more the better.
As for the quad a q6600 doesn't cost much anyway so there's no point saving 50 bucks or something and getting a dualcore instead since the extra cores will help alot with rendering if you don't have a seperate machine to render.
Whats the timing on the RAM? DDR3 is better but it also is quite a bit more expensive and not worth it for the performance gain IMO.
No sure how maya goes with SLI but but if it has no problems with it then the two will run it fine though if your not going to play any games you'd still be better off with a quadro though it would cost a bit more.
Liquid cooling is only needed if your going to overclock the system which if it's a business system then you wouldn't be doing and if it isn't then you shouldn't be doing it unless you know what your doing.
You'd also be better off with 2 hard drives so you can put the swapfile on a seperate disc which will improve performance somewhat when it has to use it, could even go for a RAID setup for optimum speed for personal use is really not needed unless you really want the extra speed.