... like your signal problems are anywhere near new. ... Maybe it really is time to reexamine your entire setup ... Best to just do it right and enjoy everything working correctly.
I started with X10 over 10 years ago, with one of the serial port "Firecracker" starter kits.
I used plug-in modules only in my first two apartments, and then bought a number of switch modules when I moved into a house. I started with the CM11A in my second apartment, and bought the CM15A when it came out.
I worked with a band-aid setup (one RR501, one TM751, a capacitor to bridge the phases, some SmartMacros that sent RF signals to turn on some lights, etc) for a long time, but decided this summer to make the system work right.
I installed an XTB-IIR, and moved my CM15A over to it. That solved my PLC signal strength issues. I taped a 19" length of (insulated!) copper electrical wire alongside the CM15A's antenna (no electrical connection - just a passive reflector). That solved my RF signal strength issues.
I was then able to clean up my AHP file, and remove a number of the macros and other things I'd put in to workaround the limitations in my system. The system has been nearly perfect for the past few weeks, and I'm very happy that I did it. I should have done it years ago.
Before returning the CM15A you bought, I would recommend you think about trying to fix the problems you have, and what it would take to do that. It might take a little effort, and you may even have to spend some money (on a booster/repeater, and/or filters, etc), but you may find that you can get away with using only a single controller, connected to a Windows PC, and also be able to take advantage of some of the newer features (SmartMacros, etc). Not to mention all of the really neat software people here have written to go along with the CM15A.