I just recently purchased a 2016 WRX and I have been out of the car audio industry for several years now. I am looking at upgrading the factory system, while retaining the OEM head-unit. The biggest problem with the system is the lack of power/volume, and secondly the non-existent bass. I want to keep everything as small and hidden as possible. I am not up to date on all of the latest gear so I was hoping to get some input from you guys. I was thinking along the lines of of either Rockford Fosgate PM100X1 freeload amps when they come out, or a PBR300X.4 under the front passenger seat. I had considered teh factory Kicker subwoofer upgrade, but I have a feeling I won't be satisfied with its output or sound quality. As far as upgrading speakers or adding a DSP I'm not sure if either would be entirely necessary to achieve what I'm looking for. If I could fit two mini amps or a 5-channel amp under the passenger seat with a small DSP that would be ideal. I may possibly have to make a flush subwoofer enclosure as well.