300-500US? Where did you get that info from?
A decent turbo usually would cost ya 3500-10,000 US depends on what size of turbo u wanna put in. Remember, the labour may cost the same as the turbo itself. If I were you, I would install a Chip(if that's avail.) that specially designed for your car. Or I would put a NOS system which would cost you around 1000 CDN. Or supercharge is better for the car's engine but cost ya a bit less than the turbo. However, it all depends on how much you wanna put into your car. U could spend the price of Boxter to soup up a Civic that beats a 911. But what's the point? It's all up to you.