For the Mk4 with two bulb arrangements, you will need a pair of H7 for dipped, and a pair of H3 for main. Dual filimented bulb clusters of course need the H4 sets.
I'm not liking un-named ebay bulbs much and i have tried them once just to see if my theories were correct. They were some cheap "Xenon" bulb that had a nice blue tint like the colour of 5000k or more proper HIDs have. They lasted me a good few summer months where i only needed them for a couple of nights a week, suffice to say they faded and dimmed substantially and really thought at the time it was my eyes playing tricks on me. This is the same experience with my friend who had a Lexus. His got so bad so quickly we couldnt see much in the dark to the extent it was hazardous to drive.
That being said, i used and would recommend Osram Cool Blue, they give a decent light output but not much white/blue look, you really cant have both with normal filiment bulbs. I had a set of H4 which lasted me for a couple years, up untill the point i wrote off my car!

There should be some bargins on ebay for these, i've not come across any fakes yet but as always beware.
HID are the way forward if you really want a white white light and nice light output, got some 4200k or 5000k kits