I havent used the AVR-790 yet (slow economy means I don't necessarily get to see every year's new model ), but I've put in a ton of Denon 700, 800, and 900 series receivers. They're definitely excellent units. If you're even remotely likely to expand the system some in the future, I would agree that it's a very good idea to go a couple steps up from the entry model. Besides the additional connectivity there's always little quirks and missing features on the lower models that only become relevant or noticable when you start trying to do more (for example: speakers in other rooms running off zone 2 being unable to use any digital inputs as their source, only analog inputs, unless you went above a certain model).
I'm the lead tech for a low-voltage contractor. Which means I pretty much do just about anything related to wiring and electronics. Home theater, burglar & fire alarm systems, phone/TV, computer networks, CCTV, access control, etc. Being a small company and not specialized in one area means my job is very ill-defined with a lot of one-off situations doing new things (or different variations on the things I've done before; nothing is ever "routine"). I'm also the guy who's responsible for figuring out "impossible" situations like: We got 5 conductors left between here and the control panel, but we need 7 conductors to hook this crap up correctly and it would take over half a day to get another wire across the warehouse without a lift, what the fuck do we do now? I dunno, but it's Ryan's problem now.