Sundowns are fantastic subs. Even the 8" ones can hang in with some of the better name brand 12"s. Unfortunately Sundown doesn't make any shallow ones to my knowledge. Fi is arguable one of the best brands out there right now for subs but they will definitely cost you. I'd rate polk above alpine/pioneer but Fi quality. Whatever you do do NOT under any circumstances waste your money on a set of sonys... Right now the best shallow mount out there is the JL 13tw5-3. A friend of mine has one in the trunk of his Camaro and I have to say it is a bit better quality than the pair of 12" full size JLs that I have. Unfortunately it also costs a bit more
Not trying to bad mouth the subs you guys bought just giving out my opinion. As far as setup, as long as you keep in mind the ft^3 that the speaker needs in a box almost anything can sound good with a well built box. A lot of people I meet think that they need the biggest subs with the highest max output, when really this sub is just going in a truck cab. 10" max is all you really need when the speaker is bumping 6" under your a$$ in a small cab. max watts mean nothing, RMS is more important. Expensive speakers still sound like crap if you put them in too small of a box, and my biggest pet peeve is quality. What good is a loud subwoofer if it is so distorted you can't even hear the lyrics of your music through the garbage!
again not trying to degrade anything you guys bought. As long as it isn't sony its fine with me, I just get a little riled up over bad sound system advice so I'm trying to preemptively give good advice haha
sorry about that /rant.