To improve performance, you should get performance tires. A good performance tire in 205/60-15 will be way better than a mediocre tire in 215/55 or 225/50.
The Yokohama AVS ES100 or BF Goodrich G-Force Sport are both good high-performance summer tires that come in the right size. I've got the G-Force Sports on my Aero right now (with 15 inch rims off my old CS because the previous owner sold the 16's) and they are very stick and handle very well for the price.
You could also go with a high performance all season, such as the Yokohama AVS db2 or Bridgestone Potenza RE950, but then you'd be trading performance for some limited snow-driving ability.
The Yokohama AVS ES100 or BF Goodrich G-Force Sport are both good high-performance summer tires that come in the right size. I've got the G-Force Sports on my Aero right now (with 15 inch rims off my old CS because the previous owner sold the 16's) and they are very stick and handle very well for the price.
You could also go with a high performance all season, such as the Yokohama AVS db2 or Bridgestone Potenza RE950, but then you'd be trading performance for some limited snow-driving ability.