Even if you get a DSP thingy I'd strongly advise getting some form of measurement equipment. There is Room EQ Wizard, Omnimic, XTZ Room Analyzer, Fuzzmeasure, AudioTools (for iPad), etc. DSP is a good solution for times when you only care about one seat but with two subs you can end up with phase cancellation issues which DSP cannot solve. Use the measurement equipment to confirm you don't have any bad phase cancellation and get things as flat as you can THEN use DSP to bring down the peaks.