Hi.....mmmmmm, appear to be no differences in performance, except as follows:#9320 does not have motorized volume control,RMS wattage seems to to be identical,9320 does not have the click on start up delay, which appears to be better;the 9100 series used to go into pause on occasion, because of that function,9320 has spkr terminals , whereas the 9100 only had spkr clips for the wires,and i believe the newer version has component outputs, whereas the 9100 did not....also the 9320 has on screen menu's for the gain on the surround channels, which the 9100 lacked, and was a big DRAWBACK in setting up the rcvr......havent seen any reviews yet, but the unit seems every bit as good as the big yamaha, or the big denon which both list for close to 2500plus dollars, and retail for somewhere in the hi teen's......in my estimation, unless ur going for separates this is one of the top 10 rcvrs around.....have been told its made at the Harmon-Kardon plant, or by its asian supplier....we sell a bunch of these, with no comebacks or warranty problems......good luck
billy c