I have a Mirage BPS150 bipolar sub that can be described as a very musical subwoofer. Would it be a downgrade for me to replace it w/ a Sony SAW-M40? I've heard great things about the Sony sub, and its attractive price has given me upgrade fever. Should I try the Sony, or save my time and leave the Mirage in place? I am also interested in building a DIY sub. Is that the better option? If so, please point me in the right direction. Thanks.