Interesting ! I'll have the S5 from a friend and maybe I'll buy the S6 after some time like this the price will go down.
I wouldn't hold my breath for the S6. If the past is any indication of the future, the S6 will be a more "data center friendly" S5. By that I mean it will likely have the same BM138x chips that are in the S5, but more of them in a package that fits in a 19-inch rack cabinet. The S6 will likely have an integrated power supply of unknown quality, and it's acoustic profile is completely unknown at this time.
I wouldn't expect the S6 to be a "quantum leap" over the S5, except in terms of packaging.