heres my input since i do have a leviathan...
unless you have a MASSIVE i mean MASSIVE case your not gonna fit it in. let alone 2. you'll need a case with two 120mm rear fan ports, and theres not many case out there if any at all that has that. and the case would be like too tall.
Unless you have water cooling you won't fit a large cpu cooler on it like a thermalright 120.
i water cool my q6600 and clock it to qx6850 specs. yes i know i can go higher, but i don't want to ok

runs @3ghz at 30degrees room temp at 25 <-- these are temps i like.
when i was building it i have to take the damn thing out like 5 times to route cables around it cause theres so little room to work with. and i have a thermaltake kandalf LCS and thats a huge case... weights around 40kg all up with everything inside too lol

(so no good to hall around to LANs)
also i believe you can sli the cards... just that theres no case to fit the two radiators is all.
else why the heck is there a sli bridge on the card? unless they cbf to remove it. (actually theres 2 sli bridges. one is for something in the future nvidia might be doing something else with that, not sure)
when i read the tomshardware review i though there would be like no sli bridge etc too.
anyway, i don't have the money for 2 so i don't know if sli works for these cards and i don't know why you need 2. one is FAST enough.
ohhh if you live in melbourne and gonna get the leviathan... cheapest i got quoted was $1,195 at centrecom
i got alittle ripped off on mine
🙁 got it for $1,275 at scorptech
also if you get a q6600 get one that uses the new G0 stepping... much cooler!
and you can pick one up for about $335 in melbounre
mate actually uses staticice to find the prices lol... http://www.staticice.com.au/
ohhh and if you have a little money left over get the WD raptor hard drive/s
😉
i love my... looks nice when you see the hard drive spin and stuff inside.
if you have anymore questions about the leviathan, ask, i might be able to answer them for you.