I vote for going concave all around. Don't settle for less and getting your fenders worked on to fit them isn't that bad.

 

my setup
17x8+47
17x9+44

 

Unless you don't plan on lowering you car much, I would vote against the concave wheels on all four corners... unless you decide on getting wide front fenders. I already occasionally rub in the front with non-concave wheels already.

Keith