Another option is a nice sound card (avoid Creative labs sound blasters at all costs) hooked up to a nice amp or some biamplified speakers.

Biamps are great as they minimize distortion by not sending the wrong frequency sound to the speaker. ie a tweeter will produce distortion if it is asked to make bass noises and visa versa. With biamps you have performed your crossover filtering before the signal get to the speaker giving you a much nicer reproduction.