what is the temp of the air you are pulling into your cabinet? mine was around the same in my closet when i was using a single 4" fan, i ended up buying a tent and a 6" vortex, you can see a link to my grow in my sig... i think my main issue before was i was using a passive intake, and it wasnt enough to cool my 600w... in order for my temps to be stable my intake air has to be within range, i keep it 75 in the room, it stays 75 in the tent... im also using my 4" now to intake air, then im pushing air through my hood and out the window... also, where are you exhausting at, you need to get that out of whatever room you are pulling your intake from, it will make keeping it cool easier on you... also, if you would like more assistance from me, please shoot me a PM, or give me a shout in IRC... im about to go to sleep here shortly and i will totally forget everything... basically though, for more help we gotta know where that air is comin from, how cool it is, and where it is going... dont worry man, you will get it sorted...
edited to add:
if youre temp your pullin into that room is any higher than high 70's the results will not be good and you may need to get an AC unit... as for where you can find a blower exhaust, just get a 4" or 6" inline fan and make the ductwork...