Just a couple of suggestions/hints:
* MythTV quality - there is a setting somewhere (recording group?) in the mythtv frontend that allows you to select the quality setting for LiveTV etc. Maybe this will help.
* VoIP - I came over this forum post dealing with setting up a Gigaset handset using asterisk http://forums.whirlpool.net.au/forum-replies-archive.cfm/927308.html, that guy is also in Australia.
I just purchased a Gigaset (S675IP) that I am hoping to set up with LMCE/Asterisk when I get the time.
* Extra keyboard keys - I suppose the procedure for setting up extra mouse buttons could work for this case too (haven't tried it myself, so don't shoot me ). It is the wiki : http://wiki.linuxmce.org/index.php/Use_Additional_Mouse_Buttons