Yeah, I'll give you a bump, as, IMO, you ask a great question. Unfortunately, I cannot help you with your specific questions about zones and such.
I will say, I did run a Yamaha RX-V1800 for some time, and then bought an Onkyo TX-NR809. Based on the comparison of those two, I would agree with your assessment of the Yamaha house sound. I did immediately notice better audio quality both for two-channel music and home theater. If a current Onkyo model at a similar price point provides the zone flexibility you need, you might pick one up from Amazon and if you don't like it you can return it. I use my Onkyo with a separate two-channel amp for the front L/R speakers, and it seems pretty darn good sounding to me, for an A/V receiver-based setup.
I will say, I did run a Yamaha RX-V1800 for some time, and then bought an Onkyo TX-NR809. Based on the comparison of those two, I would agree with your assessment of the Yamaha house sound. I did immediately notice better audio quality both for two-channel music and home theater. If a current Onkyo model at a similar price point provides the zone flexibility you need, you might pick one up from Amazon and if you don't like it you can return it. I use my Onkyo with a separate two-channel amp for the front L/R speakers, and it seems pretty darn good sounding to me, for an A/V receiver-based setup.