3 channel amps

Uhm no the 3 channel is its own independent line of signal.

You must have an AV tool that can at least do multichannel audio even if it's just Surround Sound or else there's no need for the centre channel signal for an amp @jbuhl 

As others mentioned, a 3 channel amplifier has three separate channels or amps on board. This would be handy for example when powering your front stereo pair plus a center channel speaker. Then you could power your surround channels with lesser amplification (maybe the part build in to an A/V receiver) since those are less demanding than the 3 front speakers.

I have used a 3 channel Parasound amp at some point, just to power a stereo setup with no center channel. It works fine. You are obviously "wasting" the circuitry in that center channel but if you find a good deal on a good amp, it might still be worthwhile. 

Or it could be used for a L+R and a passive subwoofer.

Ok I have a nice B&W HTM2 Center in my AV rig that is sinfully under utilized. I am toying with the idea of moving that into my 2 channel system with this 3 channel Classe.  What frequency is transmitted to the 3rd channel? In my 2 channel set is just a Rogue RP-1.  I would just be listening to stereo recordings.   Maybe a center for 2 channel rig doesn’t make sense?    I realize when I do that I no longer have 2 channel. 

Apologies for my poor understanding. 

Update:  I just looked on the back panel of the Classe.  It appears I would need a AV type pre section for the 3rd channel?  Or If I come off the line2 of my Rogue then I would have to choose either the left or right channel ?

Hey OP,

The center channel is not really used unless you have a home theater processor.  Even then the default is to not use it unless you enable some sort of matrix mode like Dolby Prologic or something else which tries to use "extra" speakers in a home theater by some artificial processing.  Some of it can sound quite nice but I think if you have a center you shouldn't force yourself to use it elsewhere.  Sell it and reduce your hassle.