18's are pretty common on the e85, I swapped from 17s to 18s on to non-RFTs on my 2003 2.5 and whilst the cornering feel and ride are slightly different there was surprisingly little deterioration in ride. Depending on the wheels you may have to check the offset is OK (offsets are always a mystery to me) but there are some pretty knowledgeable people here so I'm sure someone can advise if needed.