I went from stock steelie 15s to 16s and HR rated tires and noticed a big diff. in ride feel. I can only imagine what 18s would do. I agree that 18s would look great, but my old butt wouldn't like the stiff ride day in/day out. I do a lot of hwy. driving, so I still like some comfort. As far as handling now, I can't complain. I have to take a "naughty hard" turn to get the tires to roll over in a disagreeable way. I try not to be :rick:
If I did anything else for handling, it would be to upgrade the stock struts/springs (with slight drop) because they are the weak link. If you're into performance, don't forget to pick up a TSX rear sway. I still swear by mine. Best $50 you'll spend.