Been using my Hex w/ 5870 for a day now, doing all my installations (Final Cut Studio, Adobe, etc, etc) and I'm amazed how quiet this Mac is. I've got it elevated beside my desk and don't hear anything. The first time I booted, I thought it didn't turn on b/c it was silent. Needless to say, I was worried about reports of the 5870 sound levels, but I couldn't be happier with mine. It's a lot quieter than the 2008/2009 Mac Pro's we use in my workplace. To be fair, though, my work suite can get pretty hot at times. I've also had no problems with monitor sleep flakiness so far. I've only got my 24" Samsung attached (MDP > DVI) at this point. My 30" Dell is waiting on the sidelines until I have everything installed and my desk cleaned up (fun). Next step is to add my SSD and 3 x 8GB of OWC RAM, then clone my fresh system from mechanical to the SSD (with the exception of the Home folder). I'm extremely happy to report I have no "popping" sounds from the audio out.