I've obtained more of my own answer. The Xantech distributor called me back in about an hour yesterday. Very nice guy, very helpful. he called Xantech and they told him the Harmony RF Extender itself can be connected to a rear IR port with a proper 3.5 mm mono patch cord. Interesting that Xantech would say that and Harmony wouldn't. So I purchased the RF extender last night. It's a fairly small product, a compact ac to dc converter for the plug, a small lightweight, IR blaster that has a spot for 4 3.5 mm plugs labeled A-D and 4 x 2 mini IR flashers. The store I purchased the RF extender from did not have any 3.5 mono patch cords, and Radio Shack was closed by the time I got there yesterday. I haven't had time to see if the patch cords do indeed work but I don't see why not. According to Logitech you can set up the Extender in either a "blaster" mode and place it where it can see all the IR receivers on the from of your equipment. Or you can set up the flashers and place them over the IR receivers. I didn't have time to try either last night. I'll try it with the patch cords tonight if I have time (but got to see that new Lost episode). I'm sure I'll still need a Xantech 794-10 to make it talk to the 990 but first things first.