Too many choices is stopping me buying! someone tell me what to do
Given that you need to buy now by the sounds of it and upgrade again when the 4000 series arrives I would just get a 3600 - it will give you a 25% or so performance boost over the 3770k and won't lose that much (max £40 or so) when you come to sell it later....
if it was a purchase now and never update upgrade then spend the extra and get a 3900x...