Sorry but 19s on a cav just look crap in my opinion. 18s at max will be nice before your ripping the wings and arches out.
agree'd... they just look stupidly big... like its trying to pretend to be some kind of sports car.
They look disproportionate to the car.
a tasty set of 18's with some sensible rubber on them, will ride better, and wont kill the car.
Theres a good chance, that you could get 18's that would fit pretty much identical to the original wheels on the cavalier (as long as your offset was pretty damn close)
225/35/18 would actually present the EXACT same rolling radius as a standard cavalier 195/60/15 wheel. The only problem you'd come across there would be width. 215 will fit better width wise.. but your either going to be slightly too small at 35 profile, or slightly too large at 40 profile
http://www.miata.net/garage/tirecalc.html
215/35/18 is only going to put your speedo out by 1% though, and in theory you'd notice very little difference (thats only 1mph difference at 100mph) and 215's will fit on a cavalier perfectly, with no modification of any kind... providing your offset is somewhere between 42-49
I used to use 215/40/17's on my CDX and they were spot on, never had any problems clearing any part of the car. They were on a 42 offset