Re-read thru all the posts and I don't see any comments about the fan speed on the actual video card, just other case fans. Is it possible that you didn't reconnect the fan on the video card or perhaps plugged it in backwards. Did you boot up the computer without the side panel of the case and visually see the video card fan spinning? If it was spinning, did you hear it speed up when you went into a 3D app? If you GPU is naked now, take a look and see if it looks concaved at all. Maybe Nvidia's GPUs are coming out too flat and need a nice thick goop. You could try lapping both your GPU and your heatsink. As long as you don't slip and sand your VC's PCB you should be ok!
Just an FYI, last year I took off my stock cooler from my old 4600ti to redo it with AS2 or AS3, can remember which one. I had nothing to monitor temps, but my card would not overclock at all after the paste swap so it's safe to say that the temps were significantly higher. Lapped both and put the heatsink back on with Arctic Silver Epoxy. The card would then do 340 core stable when it would only do 320 with the stock paste and only 300 when redone with AS3 without lapping. Either the lapping or the Epoxy solved my problem. It could be either, but I lean towards the lapping. I've lapped every single one of my CPUS over the past five years or so, never killed one, and the temps have always dropped from 2c - 4c under load.