I discovered what the 5 extra solder points meant for a socket were for, if you wire 4 push buttons up to them you can control the relay toggling direct without having to use the remote.
Couldn't find any lines/solder points that would facilitate jumpers to select button=toggle or button=on outputs though
Looks like I'll be buying the 12-button kit sometime then, which means a wireless iRiver remote will be more expensive.