>>The amp, which is installed very snugly under the passenger seat, gets burning hot.

Depends what you mean by "burning hot". It is not unusual for an amp to get warm, but if it is getting so hot that you cannot lay your hand on it and hold it there, then that is too hot.

>> Now with a higher grade fuse...

This is not a good idea. If you are popping the original fuses, then something is wrong. By putting a heavier fuse in, all you are doing is setting yourself up for a fire.

>>Do I just need more air circulation?

Depends on how much you have now. At a minimum you should have an inch of free air all around, and not be in a sealed encosure.

My strong recommendation is that you have this setup looked at and diagnosed by a professional installer. I think you could be headed for very serious trouble here.

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"