The Plinius is a descent enough sounding amp. It's a bit better than the Krell, Aragon, Classe, McCormack,and Bryston HT dedicated amps, that's definite! If you like the sound of that Krell 5 channel, the Plinius will have a similar sound, only more refined by a bit, with better soundstaging, fuller midrange, and better musicality! The Brystons aren't that great really! They're strong enough, with good body and strong bass...but theyr'e rolled of a bit, softer, added warmth, etc. They're OK, nothing that special in my oppinion. You'll probably be happy with the Plinius well enough, yes. It's better than a lot of choices you could do for the money. The Plinius is almost as good as the perfomance level of amps like the Pass X150/250, Older Theshold T200/400's, CODA model 11 and higher...You should be fine.
For 3 channel amp in the future, you could stick with Krell 3 channel 250a or McCormack HT 3 channel, and have similar sound. Aragon 8008BB X 3, and similar will also work. Good luck