I don't see any reason why this wouldn't work, but I thought I'd run it past you clever lot to see what you think: I've got a 27 inch iMac on order (with the 680mx), and I've also got an old 1080p monitor lying around. If I used the old monitor to play games (connected as an secondary display, not mirrored) would I get better performance (assuming native resolution on both monitors) than playing on the iMac screen? Or would there be issues with setting the external display as the 'primary' display? It's not something I plan on doing often (maybe for very graphically intensive games), it's really more of a random thought that popped in to my head. Interested to hear your thoughts, Cheers!