How many audio systems do you have in your home?

Too many!

Three systems and expanding. I have my primary two-channel rig in a dedicated room. Then I have a modest HT system in my family room which is primarily movies and occasional background music. Then there's a simple system in the basement for my two children to listen to while they play. My son, age 11, is getting ready to put together a budget system for his room too, mainly from my older gear. Oh, I also have a decent system at my office. Hmmmm, maybe I'm showing signs of a serious problem. ;-)

I would vote for the budget minded systems as opposed to running speakers from the main. Primary reason is the ability to control/manage the music without having to run somewhere to do it. Another reason is that your family has more options to listen to what they want, when they want, where they want. Kids like that, as do Moms and Dads.

Since these are not rooms for serious listening sessions, you could equip them quite decently for not a lot of money. Thanks to Audiogon and ebay, there's a great choice of decent sounding, affordable gear. A plus side is that should a component fail in one system, you can move something from another. Putting together a couple of budget systems might even be a lot of fun.

Two systems for me.

Main system with best audio gear in best listening room.
Second system of spare audio gear which is also very useful for burning in/testing new gear/cables before insertion into main system.

3 not counting home theatre