Skyfake - I bought one 6600K and it did 5ghz 1,32v 32m win7, had a second chip for a friend I bought pretested that did 4,8ghz 1,32v Geekbench and have an ES that does far worse - a lot depends on luck, some guys buy pretested at forums, but on what I see at biggest german cpu market for used stuff, average 6700K needs 1,3v for 4,5ghz prime. You go higher, scaling and temps get worse, more volts needed for each 100mhz upwards than for the 100mhz you went up before. As said, I would not buy, this is decision each guy makes alone, but I accept the simple fact that these are cpus that are not bad^^ - good luck at next cpu, maybe you find a gem
And now btt, enough said from my side