The very best performance you'll get for that money are the Audioengine A2 speakers - see here
for more details on these recently five-star rated pair.
If you're after a more integrated docking/charging solution with a remote, the two best options we've tested at that price are the Logitech Pure-Fi Anywhere system, our current Award winner in this category. Ideal if you want portable as well as mains-only use. More here.
A more recent option is Klipsch's iGroove SXT (read the review here
) - a more bass-heavy alternative to the Logitech, but mains-only.