If you are going to really push the thing, a fan would be a good idea.

I had a Pioneer SA-1270 on the floor u on its side running into 2.3 ohms, and cranked quite often. Without the fan, which was a breeze box type, it would start smelling like an overheated iron. I am surprised it survived.

If you are running into eight ohms you probably don't have to worry.

At the very worst you'll have to get one of those little muffin fans and tape it or whatever to the top, the circulation it induces should be as good as the convection the amp was designed for.

Run it a while and feel it, if it is hot get a fan.