Here is what I have going on.
JL 300/4 & 500/1 and 1.5 Farad Cap.
I'm in Arizona and so far no heat issue... but I image if I play it loud for a long period during a 100+ degree day I may have an issue.
In the rear wheel well there is a vent (right below where the CAP is) to the outside, so I suspect there is some air movement. I suspect I may have to add a fan to help with air movement, but so far its been ok.
This location does suck for making adjustments... but usually once you dial it in your good for the life of the install.