Can I mismatch subs?

Personally, I think as long as both are good subs, this will help even out the bass in your room. The minus is you have 2 subs to move around and try to integrate with your main speakers. 2 crossovers, 2 volumes, and 2 placements. They probably both have 2 different sets of strengths. It might depend upon why you are thinking of adding another sub. More bass, or even bass,etc. I'm sorry if I've raised more questions than I've answered but you didn't give us much info. good luck. Dan

Subs in the same series will generally work well together. I think a second smaller sub will improve your system.