What is it you feel the current Denon AVR isn't accomplishing? What is the "problem" you would like to improve?
A vague idea that things could be better, ie achieving a speakers potential, is a tough thing to address.
Amplification as a general rule doesn't improve/change/modify the sound. Amps should be neutral and simply give you the opportunity to play a source "louder" without distortion.
Most of the Denon AVRs all fit the same form factor, ie they are the same width, height and depth. You could increase your raw power per channel without changing the form factor. I moved from a Denon AVR roughly in the same power range as your 1400H up to one that is over 200wpc and its exactly the same size. Doesn't sound a bit different, except it can drive more sound pressure level if I choose. I made the change because I upgraded my speakers. My old ones were an 8 ohm load and my new ones are a 4 ohm load (give or take). I wanted something that was tested and approved for that new load.