From reading the starting post - If you already have AHP and a CM15a, and do not have range issues, just tell the CM15 to transceive whatever additional HC's you want, then use the PalmPad.
If you do have that setup and if you do have range problems, you could try a SR73a (Smart Repeater) that repeats all RF. They're about $50 on eBay.
If you don't have AHP and a CM15a, you can get the setup from x10 for $50 (and free shipping) - make sure you talk to the order people and get AHP with all 4 plugins (even if you don't need them - just install what you need) and the CM15a.
Or you can buy multiple RR501's (3-pak on eBay for $25) - one for each HC you want. (the 501's are polite, the 751's aren't)
Or, you can get a V572RF32 ($100 @wglDesigns.com) - and if you do make sure you get this part number/kit - has everything and transceives all Housecodes and security devices. (We're currently working an issue with an rogue repeated A1 signal - but other than that, it receives all RF and converts to PLCs - and it's software lets you include/exclude any/all HC's)
I hope that helps a bit!