Can I use 2 two channel amps to run a 3 channel system? leaving one side of an amp unused

Can I use 2 two channel amps to run a 3 channel system (left, right and center), leaving one side of an amp unused?
If it is a solid state amp it should be no problem. If it is a tube amp you will need a dummy load resistor. To be safe whether it is a solid state or tube amp you should get one of these !
What will you do with the unused stereo channel? Yes, a dummy load is the solution, but you'll be missing out on the full audio mix.

A possible setup could be:
Amp 1... L R 
Amp 2... sum the 2 channels to the middle speaker.

Any thoughts?

If the signal is a center channel output from a AVR wouldn't it be summed? 
The signal will be for a center channel from an AVR. Wouldn't the summed power be too much to the center?
If a tube amp you might be able to remove the input tube of the unused channel- that would remove the need for a dummy load at the output (which is not needed on all tube amps BTW). You might also be able to remove the output tubes of that channel as well- but in this regard I would check with the manufacturer.
The amp is a bel canto ref500s.
Many Class D can oscilliate without a load, use a dummy resisitor or find a mono Ice amplifier. 

Dave and Troy
Audio Doctor NJ
Post removed 
I've been doing this for years. I have a Bryston 2.5 SST2 for the Aerial 5T's and an old 200 wpc Forte 6 using one channel for the Aerial CC-3 center. It's been powering the center for close to 10 years.
The power (volume) from the center channel output is controlled within the AVR setting to balance center channel with L & R.
The simple solution would be to bridge the amp and reduce the center channel level 3-6db.  Unfortunately that amp cannot be bridged.   I would contact Bel Canto and ask if there is any issue just using one channel and if you should use a dummy load on the other.  
You should not sum up the left and right channels and feed it into one speaker.    The outputs from each channel on the amp are low impedance and there is a good chance they would "interact with each other" and short (or other bad things).   

You will need to use a stereo to mono converter.    This isolates the 2 channels and combines them to power one speaker.
As per mcreyn's suggestion, I contacted bel canto and they responded immediately. I was told "there should be no problem using one channel. Just don't drive that channel and no load needed."

Thanks to everyone for their feedback.