OK, some good news on this. First, ASUS has issued me an RMA # for the GTX 460, and I'm shipping it off Monday. We'll see if they'll replace it, and whatever the outcome, I'll report back here.
Next line of good news - the Gigabyte HD 5870 (that was an expensive card when it came out, the one with eyefinity) is apparently alright after all. Turns out there was a BIOS update for that specific card, actually 2 updates. One for Samsung RAM boards, and another for boards made with Hynix RAM. Guess what the BIOS update was addressing? VIDEO PLAYBACK. Yep. Looks to have fixed it so far. I'm torture testing it right now; ripped the other GPU out of the rig, so only that one in there, and running Collatz full bore, + a Netflix streaming video, + a website with a looping flash video at the same time. Afterburner shows the GPU usage pegged @ 99% the last 1/2 hour, and Temp is 74C.
@ JPM - yes, I have to admit it looks like the Gigabyte was a good product, and just needed an update. Time will tell if that's all it is, but I'm hoping!