I have just seen another make called Shad which seems much cheaper than GIVI or Motech
I wouldnt go for Shad at all. IMHO way inferior quality and look. I have a Givi (E460, built in tail light) but it came with the bike. I did fit the metal rack on top (for tent and sleeping bags) and dont even think to do it the way they tell you to or you can ruin your case! If anybody wants my experience with that (not many, I guess), I will be pleased to help.
Without the case the the monorack looks "quite good" (I know, it always looks shite) on the bike (nor too tall, neither too far back) but I had to take out the back rest because the pillion was pushed forward.
Cheers