Its a honda, quit rolling on 18's.
There are many 18x7 wheels out there, considering I see a ton in the subaru community, but I'm not sure how many wheels there are in the correct offset and bolt pattern.
Couple that with the fact that it will probably be even more difficult to find a relatively lightweight wheel and tire combination in that size, basically sums up the reason why you shouldn't be on 18's.
The Honda was made to be a lightweight car, and thats about the only thing that honda has going for it in the performance aspect. The suspension isn't setup for such heavy rotational mass.
Go with a 17x7 lightweight wheel like Enkei RPF1's, SSR Competitions, Volks, etc. You'll get more looks that way.