just my opinion.. I always thought my 18 sounded louder to the ear when it was inverted.. felt like it moved more air and was able to play a little lower, cleaner than when it was in the box
before I had my amp o-scoped it ran hot and I inverted it, never smelled it again then got it o-scoped and it never got hot
so yes they will run cooler, with 4 18's out of the box inverted they will lower the tuning and overall I'd say you will like it better
also easier to wire
and if your motors are sexy enough thats more woofer porn