Nice clean install! How the bass response from those speakers? I went with a set of Alpines and there is less bass than I was expecting. I'm not looking for much, but more than my phone puts out would be nice. Lol.
1, You are correct, Alpines don't really emphasize bass, they generally are best paired with a subwoofer for more accurate sound.
2, As with any speaker, it is best to have the surface they are mounted to sealed from front to back so the sound wave from the back doesn't cancel out the sound wave from the front.
3, Make sure you are wired in-phase. The positives and negatives are correct from the amp to the speaker and make sure any splices don't get you crossed. (I've even found speakers wired incorrectly out of the box) As a test, hook up one speaker backwards and see if you have more bass, if you do, something is wrong somewhere. You can leave it as is, or go through and find where it's crossed and fix it.