A quality sound card would not be much of a benefit without a decent pair of PC speakers. Most PC speakers are magnetically shielded so that it does not interfere with your monitor, but there are some budget speakers out there that are not shielded, so check before you buy. If you are just going to use the speakers for basic sound and music and are not one of those people who play CDs on a PC then you can get away with a budget PC speaker. However, if you play games and CD's then you should consider a speaker system with a sub-woofer. These would produce high quality sound suitable for most tasks.
Logitech S120 2.0 Multimedia Speakers
Cyber Acoustics Subwoofer Satellite System (CA-3602a)
Logitech Speaker System Z623