Yeah there is definitely a lot of cheap & poor quality products out there when you search on ebay or amazon however I watched this video today and it showed the light output and beam patter from 15 of the more well established products, its real interesting...
https://www.youtube.com/watch?v=SQF5ESBHLrw&t=1
The one that came out top offered double the light output from a good standard halogen bulb with just as good beam pattern. The one thing annoys me with my 2.8 FL QS is the poor dipped beam lighting, its verging on dangerous now when dealing with modern high power HID & LED lights coming the other direction.
I think they pull about 50w the LED replacements and most come with heatsinks and/or fans to cool them down. Be keen to know if this would all fit behind the dust cover on the back of the headlight.