Interesting product. Marantz should have come out with such product earlier.
6012 is more value for $$$. But when you buying 7012 and above... those level usually do not talk about value for $$$.. and more on what sound you fancy...

Well.. this need lots of experiences to share.. Here is some from my personal experiences.

For movies, example with AVR type of sounds, There are 3 important things..

(1) Speakers that capable to produce big and heavy sound (English: bigger speakers + low freq). In this case, floorstander (front speakers) also always win hands down. Try best to buy biggest center speakers as well. Real and surround speakers IMO, not important.
(2) The digital processing effect. In this case, Marantz is actually not the best. Pioneer LX series with its exaggerated effect (higher level of distortion) is great for most action pack movies, but not high quality music video, which is Marantz domain.
(3) If you have entry level to basic mainstream level speakers, Pioneer LX is better for movies (except high quality music video). But if you lucky enough to have better speakers such as high end series, go for 7012 or Marantz pre/power separate. Even movies are good (high quality type), with different effects from the Pioneer LX (ajimonoto type).

* Focal Electra series and above is consider high end sound.

For movies + stereo music;

(1) Suggest you to always get another stereo amp that can do AV bypass. Stereo amp is all about lowest possible distortion (no short cut, only pure high quality design and components), where any tiny digital effects will be killing it. All AVR amp fail on stereo music, where Pioneer LX fail very badly. Marantz PM800x series stereo amp are not bad, able to drive big speaker also.

Hope it help...

6012 use traditional avr amp layout.
7012 use separate left right amp layout. probably got fan