So on the drive back from visiting my family, I had plenty of time to think of "what could be wrong". When I tell you that right now my system sounds worse than the OEM non-bose, I'm not kidding.
When I got home I cranked the stereo to max (40) and used the DMM to test the voltage on the RCAs. Sure enough, 2v just like the specs on the HU say. I also put a brass brush bit in my dremel and took it down to a nice high gloss shine around the grounding nut. Tested the ground point with DMM and it's good (it was good before I took the dremel to it). Amp seems to be getting the proper signal, and putting out the expected power. The only other thing left is either the sub itself or the lamp cord that was used to connect to the inside of the terminals to the sub. I expected at least some decent gauge speaker wire in there?
It looked to be soldered up well when I put the sub in there. I'm not sure if I want to go and take the speaker out and re-solder in some 12ga wire like I did for the rest of the car.
I just don't get it... The bass I am getting is barely noticeably different than what I'm getting out of the doors.