New forged wheels change the look and handling of your car, but they are a steep one-time hit to your wallet. Prices for quality alloys usually soften in the winter when demand for summer performance gear drops.
You want to aim for these sales, but remember that the wheels are just the start. You still have to pay for mounting, balancing, and potentially new tires.
The 0% intro APR is a deadline, not free money. If you have a balance remaining after 15 months, the bank will start charging interest on whatever is left over.