Stevenp;
To get back to your original question, there is no loss in quality between a mini-jack PC connection versus the Powerlink BL 4 Full connection. You are creating more connection points with the mini-jack PC, but if a quick set-up for laptop or Beosound 6 is desired, it works well enough. That was the intention.
The above comments regarding the sound of the BL 4 in small rooms being better are true. Sonically, they will sound somewhat better when mounted upside down directly to a ceiling ( masonry or interior stud ), but then again so will any speaker mounted onto a resonating platform.
As are the comments about the BL 4000, which is a very good, all around power speaker, with more bass and treble. I did try a pair of BL 4000 around a laptop one time, which was interesting. I could hear the birds signing outside again, after a couple of weeks.