Q. What do I gain from stepping up to the 1910/790, as opposed to just buying the lower-priced AVR 1610/590 model?
A: The 1610 (aka 590) is a very full-featured entry level model that will be sufficient for most people. It has 3 HDMI inputs, full HD audio decoding, analog > digital video conversion (so you can run one HDMI cable to your TV for all sources), and the full "Audyssey suite" of MultEQ + Dynamic EQ + Dynamic Volume. The 1910 / 790 is very similar and built on the same platform / chassis. They have similar amp sections, identical processing and DAC's, etc.
The following are the "step up" features you gain from going to 1910 (aka 790):
1. The 1910 is a full 7.1 receiver. The 1610/590 is a 5.1 receiver (5 amps built in) but can be expanded to 7.1 using the "Rear/Height" pre-outs to add an external amplifier. You have your choice of 7.1 expansion methods, either PLIIx (standard 7.1 with 2 "rear" channels) or PLIIz (5.1 + 2 "height" channels).
2. The 1910 has a 4th HDMI input, and adds an extra coaxial digital audio input
3. The 1910 is spec'd for more power, 90W x 7
4. The 1910 has full video scaling, of both analog and digital video, up to 1080p, and these video settings are adjustable by input. The 1610 has no scaling, and no adjustable settings; it simply automatically converts analog video to digital, and deinterlaces 480i > 480p when doing so. Everything else goes out at the same resolution it came in.
5. The 1910 has 2-zone/2-source capability (no multizone on 1610), and the 1910 (not 790, see above) has a "room to room" remote control jack for wired control from Zone 2.
6. The 1910 has extra inputs: a Sirius input jack, a "CD" analog input, and 7.1 multichannel analog inputs
7. The 1910 has two switched power outlets on the back
