Dual Subwoofer Question

I don't think it's a good idea. It's definitely something you would want to audition before putting any money down. However, I'm not optimistic.

If it was strictly for HT effects like bombs blasting or car crashes, you could probably get away with it.

However, you stated that you will use it for music too. If it's crossed over anywhere above 35-40Hz, I would be very surprised if it wasn't noticeable.

I don't see any reason why you "must have" identical subs...should work fine as long as you have independent control over each sub.

Dave

Several technical issues could arise
Can they both x-over at same frequency?
Do they both have full adjustability on phase?
Do they both have same x-over slope?

Assumming answers to all of above are yes, then IMO, its possible, but unlikely that it would be successful. First of all, I assume you would be using one for each channel, which would make balancing the system very difficult. If each sub has different room modes (likely if different sizes), you could end up with double the number of peaks. OTOH, in the unlikely possibility that they have opposite modes, you could eliminate peaks. HIghly to extremely unlikely, but possible. Audition before you buy, for sure. The only scenario where I could conceive that it has a reasonable chance of being successful is if you used the smaller sub to supplment the L&R and the larger for the LFE channel. You would probably need to set your processor for large L&Rs, and take a high level signal from the speaker outs of your amp, and then high pass that to the L&Rs.