My Yamaha clips at 3/4 volume

The fact that it clips at 3/4 volume has nothing to do with how much power is being used.

Western,
Something doesn't add up here. Your Yamha M45 amp is rated at 180 Watts rms @ 4 ohms, into 4 ohm speakers that are efficient enough to have been successfully driven by a 10-watt rms Trends Audio T-amp! (Dingus' 2nd Agon system, Bedroom bliss with the T-Amp).

You should have way more than sufficient power to drive these speaker loads.
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Give us more details, and I'm confident one of our amazing A-gon Gurus will surely be able to help you in isolating the problem.
e.g.:
When you mention 3/4 volume, are you a) referring to the volume pot on the pre-amp, or to b)the peak power meters on the amp? If a), what peak power readings are you getting on the amp w/o failing?

Is your "Auto Class A Switch" deactivated? If not, try switching off to run in full A-B mode. (This could possibly effect handshake with pre-amp?)

What sources are you using?
Was this system ever more responsive?
What last changed?
What other components do you have to swap out for testing?

Good luck!

I'm using a Technics SL-PD867 CD player along with the amp and pre-amp. I had the volume pot on the preamp at about 2 o'clock, the left and right output levels on the amp were at 12 o'clock. I just got the M-45 and Aragon 28k, previous to this setup I was using a Yamaha A-700. I'll get it back to make a comparison.
When I checked to see if the Class A switch was activated, it wasn't. What I discovered was that both the A and B switches were both activated and the speakers are only connected to A. Could this have an effect?

Thank you Elizabeth, Rrog and Sandstone for your help.
As you can probably tell I'm somewhat of a novice when it comes to stereo equipment.