Yeah there's tons of volume controls out there. Here's what I know.....

Single volume control with no transformer is what you would use for a single set of speakers connected to a receiver used mostly by themselves.

Volume controls with a transformer allow you to connect multiple sets of speakers to a single receiver....the transformers take care of the impedence matching. This lets you use a single receiver to run multiple sets of speakers at a time.

The IR receiver part of volume controls can be very nice if you're not close to your stereo, but there are many other ways of sending an IR signal across the house. There are single wall-mounted receivers you can use, and many come with the sender side for your stereo.

I've found quite a bit of useful products at www.homecontrols.com I ended up using a Russound system in my house for multi-room audio. It lets you use separate sources and control them independently from each room. These systems tend to get a little pricey, but I liked the idea of having separate amplifiers. You might want to look at a really simple A-bus system, which will have its own amp for your secondary speakers, and will probably have the IR capability also. Good luck!