In the absence of helpful replies, I have to say the only Berlin bars I have used are the rent bars & since they are increasingly attracting unreliable & not so cute boys, the internet is a better bet for that.

If you are doing saunas, Boiler is a much better bet than Splash Club. Whilst Splash club has been refitted to a good standard, ever since they cleared out all the hookers, it has been frequented by very mature & overweight types. On the other hand, at least Boiler has something to look at.

I would find yourself a hotel near Schoneburg & just explore the bars.