Question about Bose Companion 2 Serie III

What do you want with > 20 kHz?
Very few people can hear frequencies in this range - apart from that, the whole chain has to be right.
And I doubt this with music playback via PC.

I find the sound quite ok so far.
There are certainly better ones, but then the price is usually higher.

Doesn't matter with these horns. They are simply a pair of better PC speakers. Quite ok for that. But you don't have to expect neutral sound like with studio monitors.