Also take into consideration how low you are. And also look into the tread width of the type of tire your buying. Falken tires have the smallest tread width fyi so maybe something along the lines of Nitto or Pirelli with much wider tread widths so you have the sqauared off tire.
I run 215/40/18 Falken Tires + 18" x 7" +40 Falken Rim and lowered on TRD springs. Absolutely no problems at all, although I still find the car rides pretty rough. I would rec 17" wheels. Its a good compromise between going big and comfort.