Wow, lucky you, the owner of a Denon flag ship AVR that is upgradable to XT32 though you are not interested in that. Regardless, the AVP is undoubtedly a top notch preamp with slightly outdated processing capability, but I will bet 10:1 even in a single blind test, if properly conducted, very few human beings can tell the difference between the two. You will have a much better chance, though still very low probability, to make audible gain by replacing the power amp.