Grado's SR80 series headphones are the best headphones money can buy for under $100. Bar none. It may not look as fancy as the other brands (in the same price range) it it does what it needs to - give fidelity to sound. The SR80's sound (for it's price) is as close to "expensive sound" as you can get. After these (upgrade ladder), there is very little to improve in the components. The SR80 has components which can be found in more expensive cans. You can read more reviews of the Grado SR80 here and see for yourself.
Buy Grado SR80 @ Amazon.com for only $95.00