I am currently running them open air.  I tried them in a rig but the 2nd card is too close to the 3rd card and gets throttled to 700 kh/s, even with max fan speed.  This was without the lid, when I close the lid it throttles a lot and temperatures raise 5-8 C.

Currently running 3 R9 290s with an Evga Supernova.  They seem to crash at a traditional 1000/1500 overclock though, I can only go to 947/1450.  Drops about 90 kh/s in total.  So if 3 R9 290s can run with a mild throttle, then 2 290s definitely can.

Its price is hedged against bitcoin.  As bitcoin prices rise, doge prices will lower.  If you can get 1 bitcoin for 1 million doges, and bitcoin prices raise 2x, you can only get 0.5 bitcoins for 1 million doges.  If bitcoin prices lower, doge prices will rise.  Profitability has stayed almost the same throughout this drop.

Quarks are the fundamental building blocks of matter, I'd wager trying to google rank quark will not give you the results you're looking for.

If you're a new member I suggest not using the trading website Cryptsy.  It's extremely slow, riddled with problems, and costs a lot of people a lot of money.  I'm personally going to switch over to Coins-e, but I've heard good things about Vircurex as well.