If I were you I would go the extra mile and buy a set of Audioengine speakers. They're not hifi but at least you'll get a far better sound.

You don't have to take my word for it, try them (you can send them back if you're not satisfied).

> I've come across the Cyber Acoustics CA-3892 and Logitech Z-4 which
> both have good reviews.

These were good reviews in Stereophile or similar audiophile publications?

> Any opinions on these or other suggestions?

My suggestion would be to go to a department store and buy which ever one you like best. Powered computer speakers of this type can give you a lot of hardware for little money but sound quality will inevitably be modest. Perhaps the only really relevant question concerning sound quality: is it sufficiently poor to intrude on my enjoyment of music? (talking, games and movies tend to be less demanding). This varies a lot from person to person and can also change over time if an individual gets used to hearing relatively undistorted reproduced music.