At the moment only one is connected, and its seems to keep it cool. I used a power cube from an old iPhone for the USB power connection. My Atmos system uses an auto sensing power bar. When the X4400H turns on, the bar switches other outlets for auxiliary devices to on (Fans, Blu-Ray, etc.). You may find something like that helpful.\n\nIn your case, I'd try it with the present Fans if they are above the receiver (heated air rises), and see if the X6700H gets too warm. Although at $10.99 each it's cheap insurance.\n\nI did some calculations and your set-up will get very loud with the X6700H (or X4700H).\n\nPlease let us know what speaker arrangement you decide to go with. And eventually, how it all sounds when setup.\n\nI hope this is helpful.\n\n\nI think even one 80 mm fan would be enough for a lot of people. The reason I prefer two is to make sure I can set them to the lowest speed so that I cannot hear them from where I sit.