[obobskivich]

just get another pair of A2's and have 5.1 with a spare in the closet, or 6.1 with a little re-positioning of stuff

you'll need some sort of pre-amp/processor to handle 5.1/6.1/7.1 content and send it out to your speakers, although iirc the audioengines are active, so they dont need an amp

baisclly, i'd grab a receiver, and use its multi-channel preouts (so it controls the volume of everything, and handles input/output), look at harman/kardon and onkyo, honestly I wouldn't look to spend a fortune on it, as it isn't being used as an amplifier, this is why i'm saying h/k, as they come with video scaling hardware built in, a ton of inputs, etc, and the amplifier isn't all that bad, its just a little "lightweight" for huge HT installs (50-75wpc on most models, which is good for high efficiency and blah blah, but suffice to say, it isn't a show stopper in terms of power output)