I recently made a bunch of shorting plugs for all of my unused inputs. A handful of RCA plugs, some 430 ohm resistors and a little bit of my time. I can't say that I notice any difference, but it was cheap and easy, so why not. Also, I just purchased a Manley Steelhead phono stage, and the factory recommends that all unused inputs should have them. Hmm, so why did they not supply them with the unit???? Anyway, that's what prompted me to make a bunch. Filled all the unused inputs on my ARC LS27 as well. It all still sounds as awful as it always has !! LOL (just kidding)
Cheers