We don't have any argument with switching to a Civic Si from a Corolla S based on performance. The Civic Si is the better choice for acceleration, handling and braking, though it gets lower fuel economy (25 mpg combined versus 30 mpg) and requires premium gas.
We endorse this move even though Honda softened the suspension on the 2012 model compared with previous Civic Si models, sacrificing some handling prowess. Even so, the Civic Si has greater street cred than the Corolla S, which is mechanically identical to the reliable but dull Corolla LE. In contrast, the Civic Si adds a larger, stronger engine, performance tires, larger brakes and sharper steering compared with other Civic models.
We can't help but wonder, though, how much is this going to cost? If you're trading in a 2012 Corolla, you will probably get dinged for a full year of depreciation even if you've owned it for six months or less. That will cost at least a few thousand dollars, maybe more, plus you'll have to cough up more for the Civic Si and pay extra at the pump.
If money isn't an issue, then put the pedal to the metal. If this amounts to more than pocket change for you, then you should ask yourself if the benefits justify the cost.