rears and surrounds

I'm building a new room which will be 13'x14'x 8'in the front and 10'9" in the rear. I now have a 5.1 system with di-poles for surrounds. I now want to go to 7.1.
My question is: Would another pair of di-poles be best or should i go for direct in-walls for the rears. (all paradigm studio reference speakers.)
Thanks for any input.
Roger