Personally, I'm a fan of lightweight wheels and good tires. There's a lot of nice looking "bad-ass" wheels out there, but they're almost all heavy as hell.
The stock silver five spoke from the 99 GT's is forged aluminum, weigh 17 lbs. each, and are 17" x 8". A stock Bullitt wheel is the same size but weighs ~22 lbs. each. If you swap from the Bullitt wheel to the 17 lb. wheel with a good tire mounted, your car will seriously feel different and better. It will accelerate a little quicker as you've shaved a total of 20 pounds at the wheels and you've got better traction. It will handle nicer because the lighter wheels will more easily go up and back down over bumps. It'll turn better because you have better tires and your wheels follow the road better.
The stock silver five spokes are probably the cheapest, best option, but there are plenty of other lightweight wheels out there. They're just not all forged aluminum and ~$400 off craigslist locally. But yeah, they're not the best looking light-weight wheel you could find.
I say lightweight wheels and tires. If you were gonna go FI or something wheel weight would be moot, but since you're not, wheels and tires are a huge performance benefit. Just tires alone are a cheap performance upgrade, IMHO, for what you get. Seems silly to spend a bunch of money on performance that just goes up in smoke because your tires can't use it.