Just seems you like some of the dsp/eq tweaks in the Yamaha vs the Rotel, nor do the speakers particularly care how much you spent on the amp/avr, it simply needs to be sufficient for your use. Amps on their own should be neutral (maybe flat/lifeless to you?), it's dsp/eq that largely makes the difference among avrs, not the particular "amp" section. You might like current Denon/Marantz units with the Audyssey Editor App to customize the eq the way you like, or use the Audyssey DynamicEQ/RLO features. Yamaha avrs with YPAO and their PEQ might be something you'd like, especially if already familiar with some of the Yamaha feature set.
The contour (assuming it's a loudness contour feature) on the Rotel might help, tho.