My answer was to reserve one room of the house for my MAME system, an SGI O2 set up for Quake 2 with various mods some other PCs for other tasks and my Sega Megadrive with Sonic.

Everything is hidden away in a big sideboard with monitors all along the top, and to ensure the kids can't get at any of it a nice big lock.

It's all organised nicely - doesn't even get in the way of my guitars, amps and Sonar 2 installation filling the other side of the room.

Oh yes - it is a very loud room