Hey. Let me preface everything I'm about to say with, "I'm no expert", but I figured I'd share what I know.
I have had two 890s for a few years now doing multi-zone. I've just now purchased an 890 Pro and am trying to migrate to that. Here are my thoughts and lessons learned.
First of all, having nothing to do with the 890 Pro, I'm wondering why you need the IR piped back from your basement into the zone in question. If it's just to control the TV that's physically located in the zone as opposed to all or most of your other equipment, you don't have to pipe the IR back to the zone. When programming your remote, you indicated for each device whether the device is to be controlled by your RF Extender (located in your basement) or by the Remote itself (via IR instead of RF). You want to set up the TV to be controlled by the Remote itself. Sounds like everything else is in your basement, and therefore all other equipment should be controlled by the RF Extender. So I'm betting that at this point I've opened your eyes up to something great, or I've stated the obvious and look like a dufus. 
Anyway, here's why I'm upgrading to the 890 Pro... First of all, the regular 890 is limited to 15 total devices. I do not wish to walk around from room to room with a sole remote to control everything, but on the flip side, I wanted each and every remote to be programmed identically to work in every room, so that I don't have to worry about whether at any given time I'm holding the right remote in the right room (the remotes tend to wander in our house). Well, you rapidly hit that 15-device limit if you attempt the above. Next, I didn't like the idea that each time I'd bring another room online, I have to add another RF extender to my wiring closet with IR tentacles running all over the place. And since the price of both the 890 and 890 Pro seem to be falling rapidly, paying for the expensive one is less intimidating to me now. Then the last reason why I made the move is that the software to program the 890 does not manage multiple remotes. I believe what you're technically supposed to do is create one account per remote, thereby duplicating a lot of equipment (perhaps a receiver or an HDMI matrix) on multiple accounts. What a pain in the butt. I did find a way to trick the software into thinking there's only one remote, but it kept figuring out that I had two RF extenders, and I kept having to delete the extra one that kept showing up in my account. Just pain in the butt factor here.
There are apparently other reasons to upgrade that I haven't tested yet, and that's that all RF communication for all 890 Pros in your house seems to go thru the one Harmony 890Pro that you designated as the master. The benefit of this would appear to be that the central remote knows the state of all devices, so that if one remote in the master bedroom was calling for your TiVO to be turned on, but your TiVO was already being watched in the living room by my wife, the central remote would know that it's already on and therefore *not* send the signal to the TiVO to toggle power, which would otherwise now turn it off. That's just one example of knowing state.
Unfortunately, that's all I have right now. I don't mean to hijack your thread here, but the questions this has led me to is how to move devices and activities between "rooms" in the 890 Pro software. When I logged into my 890 account and hooked up my 890 Pro, the software migrated all of my equipment to just one "room". I've added the other rooms, but they're now empty, and instead of recreating all the devices and activities in the new rooms, I'd like to simply move them over. I'm all ears on that one.
Can't think of anything else to add. Shoot me a line if you have more questions, or if you happen to know something I don't.
Thanks.
-Jim
