There are different ways to look at this, but sound quality wise, I would say there is a fairly big difference between computer speakers and home audio gear. I've never heard the Onkyo's but I have seen some reviews on them.
In the past I've tried Logitech Z680s (couldn't stand them: boomy bass, poor highs and lower mids), Klipsch ProMedia Ultra 5.1 (much better) and I've done a side-by-side comparison between the Klipsch and the Athena Micra6 (which I still own). I can tell you the Athena Micra 6 are noticeably better than the Klipsch. Of course, once you factor in the receiver, they are also more expensive.
In the past I've tried Logitech Z680s (couldn't stand them: boomy bass, poor highs and lower mids), Klipsch ProMedia Ultra 5.1 (much better) and I've done a side-by-side comparison between the Klipsch and the Athena Micra6 (which I still own). I can tell you the Athena Micra 6 are noticeably better than the Klipsch. Of course, once you factor in the receiver, they are also more expensive.