Save your money and buy the MX-900 instead. I've got both in my own home, even the wife prefers the 900 over the 890. It's not worth the constant tweaking to get the 890 setup correctly and the darn thing will have issues at least once a week.

BTW: The 890 base station will respond to RF commands from the 900, so you might actually be able to use the existing base station to send simple commands via the 890. But the macro's are stored in the 890's base station, so macros would not work in that configuration. I have not tested this other than programming 900's and 950's in my home office which would cause issues if my wife was watching TV downstairs. I was constantly changing channels, volume etc, until I reprogrammed the MX units to another receiver ID.

I think the Zwave portion is only used for Zwave devices, not standard IR to RF command sets.