I will have to disagree strongly with your opinion Vaultertrim in that changing the size of your wheels has no effects on handling. you are correct in that when a bigger alloy is used, appropriate tyres are used to keep the rolling radius the same, but to say it has no effect on handling is untrue!
First of all, I'm no expert in handling, it's a science really, and one which takes a life time to master, even the F1 handling experts get it wrong every now and then! - ask Glenn 'EssThree' and he will tell you the same.
In this case, say if the suspension is standard S3 and running on standard 17" 'Avus' wheels, anyone will tell you it's a poor handling hatchback, it just understeers everywhere when pushed hard, and the amount of roll you get when taking corners is another story. Now take the same car and put 18s on it, and it's a lot better, it still understeers, but not as much, so a definite better handling car. This is due the lower profile tyres, which give a quicker response to your steering inputs and also reduces the amount the car rolls(less tyre flex) when pushing hard - It's a small improvement, but it's still a better handling car than when it was wearing 17" wheels. Of course this can be improved on with the addition of lowered suspension, shocks and ARBs , but we're talking about wheels here.