sound quality should be identical as both use the same MultEQ XT calibration software.
IMHO -- if you are big into network streaming audio, get the newer model. It has an improve smartphone app interface, plus adds Spotify support (while deleting the sort of useless Napster/Rhapsody options) and can stream AirPlay audio to Zone 2 independent of Main Zone (the xx12 models can't do this with AirPlay, it hijacks the whole receiver). Plus the new "auto standby" feature is quite useful for when you are done streaming.
Here's a comparison....
- Both are very similar overall... they both have MultEQ XT calibration + Dynamic EQ + Dynamic Volume, an on-screen GUI that can overlay graphics on video signals, network support with AirPlay, Pandora, etc. and the ability to control via a smartphone (app) or PC (web browser). They both also have the same 3-year warranty.
- They have essentially the exact same input/output selection, not sure where you got that the 2112 has more legacy inputs. You can go to the Denon website and download the manuals and/or just look at photos of the back panels. The only change in the input/output selection is that (1) the 2113ci model drops the Denon iPod dock support, so it loses the dedicated "Dock" analog audio input + s-video input; and (2) the 2113ci moves one of the 6 HDMI inputs to the front panel (5 rear / 1 front) whereas the 2112ci has all 6 on the back.
- The 2113ci features new aesthetics, plus a redesigned (simpler) remote and GUI interface. IMO all three are an improvement, although that's a minor difference in the grand scheme.
- The 2113ci supports 4k video passthrough and can scale up to 4k
- The 2113ci has a shallower chassis (13" total depth, reduced 2" from the 15" depth of the 2112ci).
- The new xx13 models have an "Auto Standby" feature that will turn the receiver off automatically after a designated amount of time (30 or 60 minutes depending on how you set it) which is useful for when you are streaming audio and then leave the room/house.
The only major "losses" on the 2113ci is that the new, simpler remote has a few less control buttons (requiring you to dive into the GUI for certain settings) and the 2112ci had a special 2ch custom menu for if you wanted to configure different setting for 2ch audio vs. multichannel.
If you head over the xx13 owner's thread, you might want to read through my review (and/or watch the video review) of the 2113ci: http://www.avsforum.com/t/1409431/the-official-denon-avr-xx13-model-owners-thread-faq