They are all acceptable for features:
at least 3 HDMI in
On board decoding for all latest sound formats
Video transcoding to HDMI out
7.1 channel amps
a system to auto set-up my speakers (audyssey/YPAO/MCACC)
I think they all also have pre-outs but I dont see how I will ever need those
The compressed music enhancers are a nice feature
Pure direct switches on the marantz and Yamaha are nice, not sure if the Pioneer has it, but certainly nothing I'd base a decision on.
As for speakers, for the moment I only have 2. I will begin to expand that peice by peice over time. The speakers are old speakers that I bought about 15 years ago and still love. They are Signet bookshelf sl 260 B/U speakers. The brand has gone bankrupt years ago and Im not sure of the specs. I tried to look it up but had some trouble. I think the sensitivty is around 88-89 db. I'll see if I can find the owner's manual at my parent's house.
As I live in a one bedroom apt, Im not using gigantic sound fields, but it would be nice to consider that one day I may be using a larger (think average not huge - space)
I would have thought any of these would be powerful enough to drive a 5.1/7.1 system. no?