OK, I see, I missed the aftermarket cooler comment, oops! That should be better than stock. I think the 80mm fans should help, especially since a HTPC case is generally small and heats up quick. Even if on low speed, I think it would be a good addition. 80mm fans are pretty cheap anyway. The only thing you dont want is the exhaust fans stealing the air from on top, where the CPU cooler wants to get the air. But overall, I think it's a good thing. The only sure way to know is probably to try with and without the fans.