Just tried cgminer on the GTX system without the proxy running, worked ok, 240KH/s total not too bad for old Nvidia cards
I wrote a program called cudaminer which should get close to 200 kHash/s out of each individual GTX 480...
I tried cudaminer on that system, saw ~180KH/s per card, but it BSOD's after a couple of minutes -- don't think cudaminer is at fault because the 480's are old & probably have some bad procs. Getting ready to replace them with 7870's.