Welcome to the forum msinclairinork,
I don't recommend X10 because it is not reliable, and you have only very basic control. However, if that is all you can afford you may want to try it. One day though, you'll probably decide it is not worth the trouble. That is pretty much where I have ended up with X10 and I'm looking for a good replacement system.
You can control X10 directly from VoxCommando and also receive events from X10 remotes directly in VoxCommando, but you need to use the correct USB device. I don't think they still make the one I have (CM15A) so before getting something else, let us know which USB controller you are thinking of and we can try to determine if it will be compatible.
You can control all sorts of different programs from a single VC setup, and you can create as many custom setups as you want on one machine using only a single license, but it is up to you to configure it how you want and to make sure your command phrases don't overlap. You can control skype, mediamonkey, itunes, xbmc, mediaportal, JRiver etc. all from one VC config but you need to work out the logic of what happens when you say "play"
. There are various ways to deal with this. In the case of itunes and x10 this should not really be an issue anyway.
As Kalle says you can use Windows Speech to train your profile, but you can also check the "learn" button on the main VC window. The problem here is that when it misunderstands you, it will "learn" the incorrect command. It's all very "fuzzy" though.
I'm not sure if you can set the input level of the virtual mic for pocket audio, but if so try turning the level down.