500GH/s bitfury rig? How much wattage does that beast consume, bearing in mind an OC'd S3+ @ 500+ GH/s consumes ~400w?
It's over 1W/GHs by a bit, which is why I'm looking to create a couple quiet S3 space-heaters, and retire the current Bitfury space-heaters.
If it is space heaters that you REALLY want, AND you do not mind maintaining / reducing your hash-rate, you could be better served by acquiring a set of S1's, underclock & undervolt them (to output ~125 GH/s @ - and don't ask me for a link, search the forum!) and replace the fan with a couple of quieter ones in a push pull layout at full pelt, aka blue wire hack; For a tad less power for both compared to your bitfury rig, you'd be laughing!
EDIT: I am currently running a couple of bare S1 boards (neither underclocked nor undervolted) off cgminer with a fairly loud fan blowing over them and they hold their own as space heaters! Did my laundry drying rather quickly today too, so I can vouch for a couple of these archaic beasts to do the job well.