I gotta agree with Wooch...YPAO does a helluva lot more than a knowledgeable guy and a 100 dollar SPL meter could ever do as cheaply and as fast as YPAO does it. I know my old Yammie and Marantz receivers inside out, they were calibrated as good as it was going to get, delays were right, levels set with the SPL meter, etc...
When I borrowed my bro's 1400 for 2 weeks, the difference was incredibly significant. Of particular note, 1 side of my odd shaped room generally made loud treble sounds a bit too emphasized and distracting (ie: glass shattering, symbals) on the left hand side. I could never, through any level adjustments, minor sound treatments, etc, eliminate this without creating some problems somewhere else. YPAO did...what's more I never, ever in the 2 weeks had the urge to tweak a setting as I often do depending on the source.
This feature alone, in my humble opinion, is worth at least $100 because it can do so much more than an SPL meter and manual setting tweaks can. This feature also ended my decade long brand loyalty to Marantz.
Read up on all the things YPAO can do, it ain't no SPL meter. It's also probably not worth $250 dollars by itself, though.
As for the HTR-5760 and 5790 models...there are some very, very minor differences between their RX-V cousins. They both have pre-outs and all the processing and sound quality of the RX-V's though...I'd say go for them if you can get a deal. The HTR-5750 and below don't have the pre-outs, though.
One last comment...don't Denon's new models (ie: avr-3805) have an equivalent to YPAO?
If so, that makes the decision much harder. That 3805 looks like one super receiver.