This is coming from someone who's experienced a few stops since dinosaur -
You might want to use the comparisons available at http://www.pioneerelectronics.com/PUSA/Home/AV-Receivers/ch.Pioneer+Receivers.Compare
I've transitioned receivers from basic stereo (Harman Kardon mid-70s and Marantz early 90s) through composite (Yamaha around 2001) and HDMI (Onkyo 2008). Add an entry-level Harman Kardon to the latter just 4 months ago. Interest in home theater use (5.1 system since early 200s) including 3D TV and DVD (both purchased October) but music capability is primary (most recent purchase - prior to the SC-1222 - was an Onkyo CD player with better DACs).
Had some Spica speakers (TC-50s) renowned for sound stage and imagery. The recent Harman Kardon didn't have the power to drive those 4 ohm speakers and - like a fool - I decided to change speakers rather than the recently purchased AVR (found a loving buyer that can't say enough good things while driving them with monoblocks). So new Klipsch RB-82 IIs.
Just wanted to establish the extent (limited) of my bona fides before actually commenting after playing with the SC-1222 the last couple of days (I'm retired so I've had time to do that) given your predilections for dependability and sound :
Dependability: Sorry, but who knows on the 1222? D amps are relatively (compared to A/B) new. Pioneer advertises the D3 amp in the 1222 as "new." So we have the newest of the new. As chrisexv6 mentions, much lower heat could be a positive harbinger.
Sound: No qualms - go for it! As I previously mentioned, musicality is my requirement. Not having heard the 1222 prior to ordering, I was at the mercy of reviews herein. Wanted to like it, prepared not to. Always interested in comments re: the perceived "warmth" of receivers, particularly given the generally acknowledged "forward" sound of the Klipsch speakers. Not to worry - the MCACC allows calibration to meet discernment any one individual's ears (and, although still "dialing-in" my 1222, very few adjustments for mine).
No experience with the 1122-K so can't compare build quality. I like the sound (as well as the flexibility in tailoring it) and the very low operation temperature of the 1222 (due to the class D amp which the 1122 doesn't have). My experience is that change often comes in multiples (i.e., the domino effect); I think the 1222 offers greater flexibility (inputs/outputs, 4 ohm speaker capability, etc.) on future decisions.