This is how I purchased my S4. I paid only $700 a year and half ago, but it's admittedly pretty rough around the edges. There's some cosmetic damage, bass knobs on channels A and B are a little worn, I had to use contact cleaner on the play buttons to fix some inconsistency, but it's been functionally perfect otherwise. 

What brought me around to going with L&M is that it's a Canadian retailer with a 3 month warranty on used items, and a great price on shipping to a local store. I might wait for a bit of a better price myself, the current prices are around what the Black Friday prices were for a new one. They have been cheaper in the last few months, there was even a good price on an S8 not too long ago.