If it's the same Yamaha system I looked at a few months ago, then I believe it's a completely closed, proprietary system, which is not what I wanted. What I love about the CAV6.6 is that it's a very open system by the standards of this industry. The RS-232 protocol is documented on their website, so anyone can access it. I've found that many other products either use proprietary ports, or use RS-232 but refuse to give out the protocol documentation.
I am really glad that it all worked out so well, since it's a pretty big investment and AFAIK
I am the first to do this, so I was a bit nervous as to whether I might hit a brick wall or two.
As I already wrote, the only limitation with the CAV6.6 is the 12-character display, but I got around that by toggling the display between artist and title, which works fine. There is a firmware update out now which allows you to scroll up to 34 characters of text on the display. Once I get some time I will download that and maybe use that as well. You can link up CAV6.6 controllers and have a 12-room system if you want, so there are no limitations on that front. AFAIK
Russound don't allow keypads to be linked, but I have added support for that in software, so that when you adjust the volume in one room, the changes are reflected in another room. Basically anything is possible with Russound's RS-232 protocol.
FYI I am using a combination of Russound SP-H6TT, SP-S5TT, and SP-S6TT in-ceiling speakers, and they are also fantastic. I also have a Revel Ultima home theater, so I know good sound when I hear it, and the SP-H6TTs really are audiophile quality. Where it wasn't possible to install in-ceiling speakers, I went with Jamo on-wall speakers, which are OK but noticeably inferior to the Russound speakers, so I will replace them if and when I can find something better.
One more thing: I bought the speakers from http://www.bass-home.com/
and really wish I'd bought the CAV6.6 from him, too, since I would have saved a fortune. Good service and fantastic prices.