Looks sweet. For fun, you should make some benches without the 680 and see how much of an improvement it makes.
For me today, I've troubleshooted a Dell Optiplex GX520. The computer would not power on when you press the switch. The motherboard gets the power but won't boot. I checked it over and apparently the front panel was pushing the power button down and disconnected it from the motherboard. So some adjustments to the front panel fixed it. Also noticed that the fan bearings in the PSU and CPU fan were going bad so those are getting replaced. Replacement PSU ordered and replacement Dell fan(special four pin fan) ordered. So I will also be replacing the thermal paste on the CPU while I'm changing the fan. Plus from the client's request I'm upgrading the 1GB stock memory to 4GB total. Hard drive was in great condition and no work had to be done on it.
Edit: Yep. The PSU failed. Seems like it fried. Won't even turn on with my power supply tester. My spare Antec 350W ATX PSU boots the computer just fine. Well it's a good thing that the replacement will come by Thursday. The worst part is that the PSU is custom made and no other company makes them other than Dell.