poor mans multi room audio... need advice

Hello, i'm looking to setup a multi-room audio system utilizing Airplay and 2 airport express(s). I'll use my iphone and ipad for control. The two areas are my master bathroom and backyard. i already have the speakers, just need the amp.

Is there a 4 ch amp that has 4 independant always on or auto sensing inputs? I could buy 2 of those dayton T amps for each airport express but i'd rather a more powerful all in one solution.

basically i want this but dont need all those inputs and dont want to pay that price.

http://www.htd.com/Products/multi-channel-amplifiers/DMA-1240

Thanks for any advice

I was thinking about expanding later on... Garage, upstairs Den etc.

I was looking at that amp and thats probably what i'll end up doing but i was hoping for 1 amp for the entire operation. i guess they dont make 4 zone amps like the one i posted above from HTD.

Thanks