I was able to get a used isobox rack from CL for 240 delivered.
IsoBox - Sound Construction & Supply
They cost a lot new as with any rack built to be quiet.
pros:
Included fans, sensors that monitor intake and out temps. Mine currently has 3-4 servers (mostly dual e5 v1 and v2) and the intake is room temps around 72-75 F and out temps are about 95-97F.
Drops the noise down a lot. inside the rack its about 80+ dbs, outside its around 50-55 front and 60-65 db back where the hot air exhausts.
Cons:
Uses screw round holes vs squares. Not all the rack items worked well with round holes.
Lot of space in the rack is wasted due to back doors hump where the fans are taking out the hot air. I got around that by buying a shelf and laying the server on that.
Its wicked heavy but does come with coasters to roll it around
Does not have high W.A.F. (wife approval factor)
pics: