Considering the GT-c's but i was wondering what the weight of the 19" and 20" are. Are the 19's lighter than stock 18's? If they are would the acceleration be better?

 

the gt line of wheels are not very light. probably 24-26lbs.

http://www.wheelweights.net/

 

Ditto. Mole is right.

They are much better for show than for racing. Also 19"+ are not very synonymous with light either. I'm with you on liking the GT-C's though. I've got a set of 19's on the way because they look great on the car, but I'm keeping the stock 17's and putting racing tires on those for the weekend autocrossing.