You and me both Reef! I have the 4520 in my living room system and I think it does a good job. I have gotten to hear the 8801, Classe ssp800 and the MX151, though all individually, never in a side by side compare. My only gripe with the 4520 now is that I need to get up to -10db or more to start breaking into any kind of "big sound". I know some have said the unit is geared that way, and it's to be expected.
I must that my impressions of both the mx151 and the 8801 can't be taken too seriously because they were in different shops, with different speakers and different amps. I loved them both. The 151 was running through MC 200w/ch amp to a set of Dynaudio Countour5.4 and the 8801 to B&W CM9s. They both sounded great to me(though I liked the Dyn/mx combo more, but I suspect that has to do more with the Dyns, as they are some of my favorites.
The classe unit I heard was on some very expensive B&W 800CT series speakers and the entire thing was lack-luster.
I am in the same predicament as you...I know I want to try more, but am afraid to open the flood gates. I may take a set of my SEOSR once they are done and bring them to a local shop that has Denon, Mc, Anthem and Marantz on hand. If you have the opportunity to do the same, it could be a great way to decide.