Wider wheels and better tires I said should be the last resort if you are trying to spend the least amount of money. Good Wheels + Good Tires = Lots of money.
If you have a Discount or Americas tires you can go buy a set of Ultra, Extreme, or Max performance tires and try them out. They will let you bring them back for a full refund within a day or two if you don't like them just as long as you keep the mileage below 100 (I think it was 100, may be 50, but they should tell you when you buy them as each brand has a different return policy) They will work with you more if you decide to bring them back and decide to upgrade to wider wheels and tires.
If you get wider wheels, make sure you don't get wheels heavier than stock. The weight of your wheels can have a big impact on handling and acceleration. (Un-sprung weight and sprung weight work differently, which is why wheel weight has a bigger effect per pound than adding weight to the car) Getting a wider wheel that is lighter than the stock wheel will be the best option and will give you the best acceleration and handling, but the lighter the wheel the more expensive it gets. (Very expensive like BBS or Volk wheels, but they are some of the best wheels you can buy) You also need to make sure you pay attention to the weight of the tire itself as tire weight can very a lot. You could end up buying a rim that was 5 lbs lighter, but end up putting a tire on that is 5 pounds heavier and you end up with the same weight as you did before and you spent all of that money for nothing. I can't remember what the weight for the stock Gen 6 SE wheels are, but I remember them being on the heavy side, even for an OEM wheel. I think they are even heavier than the stock 18" wheels on my RX8.
Here is some interesting reading if you are interested or just want to learn a bit more.
This is a post made by someone on mini2 of his findings between a lighter and heavier wheel. The acceleration times aren't something you will really notice, but the braking results are a big increase. http://www.mini2.com/forum/first-gen...-s-long-3.html
Here is information behind the physics of how unsprung weight effects your vehicles. The lighter the wheel, the better your shocks can keep them planted to the ground as they don't have to fight against as much wheel. Put heavier wheels on and your shocks will struggle to keep the wheels from bouncing.