Cheap 2ch amp that can be controlled with iphone?

Thanks for the help. I have a sonos that i use to control a set of speakers inside. I want to use the aux out to another amp so i can use the sonos for the source for the outdoor speakers as well.
I am trying to help out my father in law and am trying to avoid buying another sonos unit($350).
If i hook them all up to the one unit i cant turn off/adjust volume on the outdoor speakers, hence the need for a seperate amp. Thoughts?

You could get an emotiva mini X amp for $219 then use a Apple airport express as your source plugging in directly to the input of the amp. Use the amps volume control on the front as a volume limiter setting it to the max volume you would want to ever hear. Use your iPhone to stream the music to the Airpot and control the volume from the iPhone, max volume will be set by the volume control on the amp incase you accidentlly swipe full blast on the phone. Also the amp has a auto sensing feature so you don't have to physically turn the amp on, just start the music and it turns itself on.