I'm talking about proper factory HID here, not retrofit/aftermarket pap (well, apart from the bulb choice).
I noticed on the "other car" the headlights were fairly dim for HIDs (infact, the MK2's lights were brighter!), so I guessed either the bulbs or ballasts were at the end of their useful life. Given OEM bulbs cost a pretty penny, I went for non-brand eBay specials just to see if it solved the problem.
After fitting, it did not, they were dim, and even worse the two "matching" bulbs I got were different colours entirely.
eBay 6k specials - mismatched colour, crap cutoff, dim
For £17 a pair, I guess you can't really argue, shame they were sh!te, but not really worth the effort of posting back.
So I ordered a pair of genuine (being the operative word, as there is lots of fakes!) Philips 85122+ bulbs (the brightest OEM bulb on the market) from
http://www.theretrofitsource.com/ 
(great comms, quick delivery, good prices, well recommended).
Passenger side eBay 6k specials, Drivers side Philips 85122+ 4.3k - notice the significantly brighter light and much sharper cutoff on the right
Both Philips 85122+ 4.3k
So as a before and after ...
Moral of this story, don't buy 6k bulbs, don't buy cheap bulbs and do buy Philips 85122+ (the + being important)
