Ok right now I have a SVS 25-31pci, I looking to add another sub to help even out the bass response. I've read that you should use the exact same subs when going multiples, then i've heard people say it does't matter, so which is true. SVS no longer makes the 25-31pci and the new PC12 NSD is out of my budget right now. So if I would get something like a used pb10 nsd or a elemental designs a2 250 would it be ok or should I hold out and save for a PC12 nsd? I'm not sure really what my room response is can't get REW signal generator to work, no sound. I have superchunks in the front corners, which help alot but I still feel I'm missing something.