I have the Hyper 212 Evo. It's a pretty good heatsink for the price, and it keeps the CPU very cool (Which is also an FX-8320). It fits fine in my Corsair Carbide 200R, which is a midtower.
From what I've looked up, the Mugen 4 is quieter and probably better at cooling your rig. It's more expensive, so that's for you to determine if the price is worth it.