My 350 from about a year ago, before I sold it for a 500, also had left/right inputs. I was told that I only needed to use one of them, however, I did buy a "Y" cable from Radio Shack which allowed me to go from one to two inputs...not sure it made any difference though.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85