I use a Mackie big knob.
I have 2 sets of powered/active mixing monitors in my control room and then I have a 3rd set of unpowered monitors running through a small peavey mark 4 PA to my drum room so they can hear talk back function (which I have on the big knob) This way I don't have to run in there every 5 minutes to tell them whats going on.
 
Its also nice to switch between monitors 1+2 in the control room while mixing and mastering.
Listening through different speakers is essential in my opinion. it gives you a great variation (between the KRK's and the JBL's = My active monitors).
 
I bought my big knob from guitar center used for 49.99 AS IS.
There was a button that needed to be sprayed out/ it wasn't staying down.
Those things are a nightmare to open up though. actually opening it up is not the problem, pulling the circuit board is.
Mackie used these cheap hex head screws that strip very easily. If your not careful, your screwed (ahh, no pun there)