I'm in the same place but not quite as well off - i have some ageing logitech X-540 speakers that have taken to a low hum when no sound going through. My office room is probably too small for something like the z906 (the inferior sibling to the Z5500)not for size but according to the reviews they are very difficult to tame. You kind of have too loud or off.
I'm looking at going to a AVR or just a 5.1 amp and a set of speakers & sub.
I have had my Z5500 for years and it is still going strong.
Paired it with a Xonar D2X soundcard t.