If you are keeping the heatsinks and all that uncovered then you shouldn't have a problem with heat. You could even cover up the heatsinks and have 40 or 60mm fans built into the cover with a rustified cog grill . The downside of this is that you do get slightly more noise and the cover has to be slightly thicker.
Check out Defyant's work, he made a mobo cover for practically every mod lol.