I'm not sure if just a fan will cut it. I don't actually know how hot it will get, but when you think that they cut the output in half to keep it cooler, it doesn't seem like a fan would do. Especially since the hot air will just blow right back onto the amp (that whole hot air rises thing. However, I'm sure you could set up something with bolts where the amp would be flipped right side up with some room to breathe. You'd just need to find long enough bolts, but that would do it. And I forgot about this before, but a few of us discussed that you could make a little spacer to fit a slightly deeper sub in that hole, so if you prefer something that'll work in this small enclosure but is a little deeper (I emphasize a little) then you could probably get that to work as well.
Thanks for the compliment. It's kind of haphazard, but I love showing it off since it was my first install!