There is almost no reason to use an 80mm fan. The sole exception is behind the motherboard, blowing at the back of the cpu. And even there, if your case could handle it, a 120mm fan would be preferable.
If you have a case that requires an 80mm fan, it's time for a new case. I made the mistake of buying two pretty good fans. I learned that quiet 80mm fans hardly push any air. 80mm fans that push adequate air are too noisy.
I figured out that Antec and Newegg had sold me an obsolete case, not worth having. I replaced my $100 Antec with a $20 NZXT and have been happy ever since.
Save your money. Learn about cases. Watch the sales. Then get a good case. Good cases are cheap these days. Do not waste your money on an 80mm fan.