I think the most "modest" or subtle body kit is OEM for coupe and Wing West W for sedan. (Of course I'm partial to the WW, I have it. )

I prefer the urethane lips kits like these. More durable than fiberglass, and you retain the OEM fitment of the stock bumpers.

If you aren't lowered...you should do that first.

I'd say 18's would look much better with a kit, but with something subtle like those two kits, you could pull it off with stock alloys if you wanted to.

Here's my WW to give you an idea: