Second system recommendations $5K budget

This may stretch your budget a bit, but I recommend that you consider a Lyngdorf 2170 integrated as your foundational piece.  They will go for about $2500 used.  The internal DAC is really good and the room perfect software really makes optimizing set up in a room easy. It will drive most speakers very nicely. The Lyngdorf, in my opinion, is head and shoulders above what I expect from Class D.  It doesn't really sound like tube, nor does it sound like what I expect from SS.  Somewhere in between perhaps.  I have one in my second system in a room with problematic accoustics and it made a world of difference.  You don't say what you intend to use as a source, but the high end input module gives you plenty of coax, optical, a USB, and even an internal MM phono inputs. the DAC is good enough that you can probably get by with a decent CD or DVD player using the Coax or USB input.  This thing is good enough to warrant stretching the budget a bit.  Used, these things are an insane value.