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.

I'd save up and get another 113 or sell and match the 112's.If your system is 2 channel then smaller is beter.Less depth but and dynamics but more tonal accuracy.Placement and integration is a bitch no matter what and mixing and matching probably isn't a good idea.I think TBI had a great ides when they offered their subs powered or passive.Passive you could get their amp/x-over box and when you added the sub it was parallel and power to each box went up.Great idea that I wish more companies would have tried.I haven't done what Eric said worked but think it would be easier wot integrate same subs.That said I like multiple drive subs.
I used to sell Velodyne and latter after I left biz I became fan of multiple drivers to move large amounts of air.Light work the Vandertseen could fill in smaller Maggies.REL did same and speed and tonal accuracy is great with Quads etc.For HT and music Martin Logan has multiple driver speedy subs.I'd like to hear the Totem Thunder with 8" and two passive 8's.But you have a deep sub and might not want to give up depth.Still two Martin Logan Descents or Depths would be my choice especially if I was doing HT.
Cheers
Chazz