Take a look at the Parasound NewClassic series: they offer an integrated amplifier (and a preamplifier variant, for others who might be interested).
I need analog bass management, so I've selected Parasound, though I will likely go the separates route. For you, the integrated amplifier's fixed Rec Out, variable (HP) Main Out, and twin sub outs (one full range and one < 80Hz) could be a very useful combination.
The physicist in me wants to say that the NewClassic 200 Integrated is the best class D available for a reasonable amount of money, but I haven't heard all of them so I'll restrain from making absolute statements. It is nevertheless a fabulously neutral, smooth integrated amplifier.
BTW, the LS50s are such nice kit - congrats!