I've got 2 FireTV sticks and a 1st Gen FireTV box. I haven't ever paid attention to how much bandwidth they use, and we don't use them for streaming very much. Mostly used to access my NAS. But I will say, I won't recommend the FireTV stick. I'd get the box, especially now with the 2nd Gen out. The stick to me doesn't seem to want to 'wake' very well... annoys me, but I will admit I've only had it running a week. My box seems much more stable. Wish I'd just gotten a new box and relegated my old one to one of the other TVs.
Hmm. I was thinking of putting the box in the LR on the main TV and running the sticks on the ones in the bedrooms. Might have to see if a store has one running as a demo to check it out.