EX comes with 16's stock.
You can get 17 and 18 through the dealer accessories. Here's the factory catalog info I have:
Info on the 17"
http://www.hondaautomotiveparts.com/...L+%2817+in.%29
17x7 J (inset 45)
tire 215/45/17 (87V)
New pressure 33 PSI F&R
See the TPMS changes and info below
The 18 looks like an upgrade for the Si, and doesn't list any other models. (I can't see why you couldn't stick it on a regular Civic though.)
Quick info I found on the 18":
http://www.hondaautomotiveparts.com/...L+%2818+in.%29
18x7 J (inset 45)
Tire 215/40/18 (89W) (Looks like a Yokohama of some sort)
New pressures 36PSI F&R
Rims are made for TPMS
New sensors will need to be "learned" to the car using a dealer level equivalent scanner if you don't reuse your old sensors.
Tire pressure sensor warning thresholds get recalibrated higher to match the new pressure specs using a dealer level equivalent scanner.
New tire information label for the door jamb.
HTH