Regarding my budget,
Either I buy the Strix 1080 from Asus (Around 750 Eur) or I go for watercooling (Approx 400 Eur) : EK is selling their last Gtx 780 Waterblock at 50 Eur each.
I will be honest, I bought this SLI a little bit blindy and it is really hard to find benchmark who compare this...