I remember when I was 20 and sold hifi, with a budget system (sub �500) we used to have the Rotel integrated, the nad integrated and the Marantz integrated amps as the 3 best sounding ones under �200 rrp.
Now, in the demo room the nad would sell 95% of the time with the Rotel selling the other 5%, even though the Marantz got stunning reviews in every magasine we never sold one. To put this into perspective we probably sold 1000 of these amps a year, and with demos not one Marantz was sold.
Everyone said it was too smooth, not airy enough and no bite at the top end.
However.......those that took the Marantz and Nad home for a home demo all bought the Marantz, well 95% of them did, the replies were "it is so much smoother, extra weight, and just as much detail, it sounds like an expensive amplifier compared with the other one."
And it did, but what you like at home while listening all night is very different to what you like in a demo, or when out, I don't go to a club or a gig and want the Merdidian sound, I go out and want the Naim sound, well OK, maybe not that <censored> harsh, but you get my point?
I would be interested to hear how much difference room correction made on your system, and how have you got the 5500 set up boundary wise etc. as that is a bass monster speaker out of the box.