I currently have the Sony WM40 sub and I'm looking to upgrade. I have $300-$400 to spend. I'm looking for a better sounding sub that is a step up from the Sony. I will be matching this with my Paradigm Atoms and the Paradigm CC-170 center. It will be used for 80-90% movies. Any suggestions? I was thinking about doing a DIY sub, if it could be done in this price range.