yeah, i used that route for awhile... the only problem i ran into was taht the 60mm - 80mm adapter wouldn't fit directly into the wind tunnel plastic casing because the outside of the 60mm part was round and didn't have a ledge to be clipped on. So I ended up gutting a old 60mm fan to get it to fit.
After all that, my 80mm's were almost to my side window, so then i made my own special side window with a vent and that dropped my temps even furthur. My fans weren't top quality, but they worked pretty well. I ran them on a controller so i could control them too.
Its a good cheap cooling solution if you want to save money, but if you have around $100 to shell out, you could get yourself some of those cooler master stacked fin heatpipes. I got some recently and my temperatures dropped after venting my rear 120mm fan directly to them, forcing air to be sucked through them. I run a good 5c cooler than using the 80mm fans and i never hit 60c on load. I only go up to like 55c and I run two less fans now.