I have the UMC-200 and have tons of issues relating to the HDMI compatibility. I think the sound and price are both fine, but I will not be buying another processor from Emotiva. They simply do not have the same resources as Onkyo, Denon, etc to test for compatibility. It is workable, but each HDMI device I plug into this has its own set of quirks. I have gotten used to it, but it definitely does not have the wife acceptance factor for usability. If you have a more basic setup, it may work better for you though.
What are you looking to gain over your Yamaha? Sound quality? Features? If it is working fine for you, I wouldn't upgrade just to get rid of the amp section.
EDIT: Also, nothing against Emotiva in general. I love my XSP-1 and am mostly happy with my XPA-5.