2 Stereo amps to be used in Mono...hookup?

No all you gain is more wattage.

" all you gain is watts, distortion goes up, damping factor is reduced, stability into low impedance’s is reduced, and current ability is reduced. "Basically" you turn a good amp into a high wattage fair amp."

Cheers George

As per manual..."Identical Signals"...
Would mean....preamp left out split to left/right input of amp.

Same for right channel....

"Same for right channel..."
Exactly. The right channel from the preamp hooks up the same way to the other amp.

I would add if using those amplifiers 'bridged to mono' is confusing... You should not do it. I agree with others writing you gain nothing and risk a lot.        
Most amplifiers stable into 4 ohm as a stereo amplifier are NOT suitable for use with 4 ohm speakers when 'bridged'. Period.I have no idea if the op speakers are actually 4 ohm? Does the op know???

ishkabibil

I forgot to ad in my last post.
If you have two of these stereo amps already, this vertical bi-amping arrangement, will give you the best sound, forget bridging.

 http://www.av2day.com/wp-content/uploads/2014/05/biamp2.jpg

Cheers George