H&r coilovers

Personally, I'd be wary of a coil-over kit for only $500. The "quality" kits I have seen are upwards of $1000 and more. I also believe in, you get what you pay for.

If you plan on doing some road racing or auto-cross, then coil-over's would be a good idea. If the car is used for a daily/weekend driver, then lowering springs might be a better option. You can get springs that lower the car anywhere from 1" to 2.5", and you should be able to maintain some good ride quality.

X2^ Just get the springs.

Those are just the springs by the way for the coilovers. Allows you to adjust the spring rate.