i think the way to go in terms of pc cases is either the antec 900 or a good HAF. something with plenty of room and lots of big fans. i own an antec 900 and the stock 200mm "big boy" fan at the top is perfect for flushing out any unwanted hot air. then the 3 stock 140mm fans help force the cool air from front to rear.
Since you have the case, do the fans connect to the mobo or the psu? The mobo that i got only has 1 input for the fan. :/ lucky everything already has a fan on it so nothing overheats. And I was already interested in that case when I saw it in stores.
If you want dirt cheap, go HAF 912. Good thing about it is that you can still manage SLI with 5770 and it only costs about 50-60 usd. For about 40 more dollars you can get the HAF 922 which is abit bigger but still Mid-tower.
they connect to the psu (although the new 900 has mobo connectors), each fan comes with a 3 way speed switch (low-med-high). i keep my front 2 fans on low, my rear fan on med and the top "bad boy" on low. i have never had a heat issue. even with my GTX470 in there and they are meant to run as hot as the sun under load.
Btw you can get a fan controller, they give you 4+ four-pin fan connectors ("mobo-powered") with speed adjuster on front panel. Some expensive ones even have LCDs which show current temp/speed.
They are connected by the PSU. If you look at the pictures (2nd row, middle picture) You can see that the Fan has a psu connection Getting the case this week.