I think a much bigger improvement to the sound will be to stop using the weak link in the AV receivers, that being the amplifier sections. You would be better off running the pre-outs (at least for the mains) into a decent 2-channel amplifier (for better stereo performance) or a good 3-channel amplifier for the 2 main speakers and the center channel speaker.
Outside of the digital processing (for the various surround modes), which you are not using if you are bringing in an analog signal; most of the AV Receivers have pretty week amplification performance. Since you already have the switchers, this would not only be the most cost effective solution to improving the sound, but may also be the easiest approach.
This being the case, I don't believe you will hear much of a difference between the Rotel and the Denon AVRs.
Outside of the digital processing (for the various surround modes), which you are not using if you are bringing in an analog signal; most of the AV Receivers have pretty week amplification performance. Since you already have the switchers, this would not only be the most cost effective solution to improving the sound, but may also be the easiest approach.
This being the case, I don't believe you will hear much of a difference between the Rotel and the Denon AVRs.