Depends what you consider to be high power? I run 500bhp and 8½s all round (no wheel arch mods required) with 245/35x18s. Job done.

Martin runs big fat tyres on the back of his, as he has 700bhp and the ability to channel 100% of the power to the rear tyres. I personally don't think you need tyres as wide as this, unless you plan the same.