Welcome to the forum, HR!
X10 has setup and provided this forum for users to share feedback and suggestions to other users. The forum is run and supported almost totally by X10 users and is occasionally visited by X10 employees themselves.
I wouldn't get another transceiver. In fact you can have problems with multiple transceivers on the HC. In your case your phases seem to be pretty X10 isolated and things are working now. I wouldn't be surprised if you had signal conflicts if you tried dimming a light while your drier was running, however.
What are the model numbers of the transceivers you have? Some don't play well with others. i.e. While the better transceivers are polite and will wait if they detect a line signal, others just plow ahead and flood the line with additional signals.
It looks like you're going to need some filters for some of your new toys. I imagine they are sucking a lot of your X10 signal. Also don't overlook the little things like laptop, cell phone and other battery charges. They can really zap your X10 signal when plugged in.
Keep in mind that should you improve your signal enough it just might make it strong enough to find its way across the phases. e.g. A good signal can bridge at the line transformer on the street. Needless to say, when your signal is able to make it across the phase your two transceivers may cause problems.
JeffVolt has several useful posts you might want to look at on the forum. Also his web links below have been helpful to many.
His X10 troubleshooting tutorials are at:
http://jvde.us/x10_troubleshooting.htmInformation on his XTB devices is available at:
http://jvde.us/xtb_index.htm