I do similar. As mentioned, I have a Squeezebox for music on my main floor and I love it, but I never purchased a second for the basement as my HTPC is connected directly to my AV gear there and it also acts as the Squeezebox server and player for the downstairs system using XBMC as an interface for movies, music, TV etc.
If not in front of the TV with my Blutooth keyboard, I use an app on my tablet, Splashtop Remote to control it via my WAN. It works well (as long as you don't try to contact them for thier useless support) and it's free if you don't want access from outside your LAN.
I also have not set up remote access through my firewall. I don't see the need for another hole when I'm always carrying some kind of portable player with me anyways, be it an iPod, tablet or my work laptop.
With great power comes Awesome irresponsibility.