I vote you stay put. Big deal, hit one button. You list very few features, and features would be the main reason to climb up the receiver ladder. The processor portion of the receiver is probably the very fastest thing to become superceded in your entire HT, and that includes video processors, remote controls, furniture, anything.
The 705 seems to have enough HDMI inputs for you, its got the XT already. While the 875 or 905 might have enough juice, I highly, highly doubt that either will have as much as your Emotiva. And of the very small set of wants you listed, power was one of them.
And... do the 875 and 905 trigger in zone 1? For if not, this will all be for nothing.
you can also set your 705 to 4 ohms settings, and that will decrease power consumption (rail voltage). However, some persons might tell you to rerun Audyssey in this case.
That's my vote.