'08 Dodge Caliber and it has aftermarket wheels with 215 35 r18 tires. What other size tiires can I get?

I drive for a living and the low profile tires are just a pain. I would like to get some tires that ride better and last longer but I need a little guidance on what size to get. I like the look of the rims but the tire needs to be taller. Any suggestions would help. Plus I do not want to spend an arm and a leg. Oh, the guy at tire discounters said that I could put 225/45/r18 on it but I was wondering if I could go taller than that.