I tried something similar a while back and it needed the volume way up and as you said, it hissed and spluttered! So, the new ones are better?
Her indoors has offered me her Sony BT radio, so may be sorted. I just have to put her VW radio/CD back in to her Polo and find a way to input her USB stick or Ipod! Doh!
EDIT- She's happy to use CDs so that's a soopa dooper Sony for mine then! Fitting kit and steering wheel control kit on the way!