larger rims DO NOT mean any change in the ride height or anythign else if you fit tyres with the correct overall tyre diameter.
it seems to me you think 15's are going to be bigger than 13's, which woudl lead me to believe that you are going to go for oversized tyres as well. which will lead to excessive wear on your wheel bearings, suspension, gearbox, engine etc..
if you are going to for larger rims, you wull have to lower your profile, or they will rub your fenders.
a good example is 185/70R13 are almost the same size as 205/45R16's in height. The rim size has increased but tyhe sidewall profile has decreased (as well as overall width)
check this site for an example of what can fit to your car: