Switch from D1S 4300K to 5000k?

I have had the Superb for 3 months now and with the recent dark nights noticed that the bulbs are a lot yellower than my the 5000k kit I was running the 'Tavia. I find 5000K better for picking up the white lines on the road edge and signs down country lanes. I'm not convinced that I haven't suffered some colour shift on the bulbs (certainly did on my first ever HID kit which was 6000k)

I know I can get 5000K bulbs for D1S but proper Osram CBI 5000K are expensive for a pair. Cheap ones can be picked up for less than £20 (with questionable outputs and quality!). Kaibird ones can be picked up for £55 a pair but I've nto heard of them before.

Or get some Xenarc CBI 5000k of unknown origin: http://www.ebay.co.uk/itm/2X-OSRAM-Xenarc-COOL-BLUE-XENON-D1S-BULBS-LAMPS-HEADLIGH-5000K-DUO-PACK-BMW-VW-/121114928304?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item1c330324b0

Has anyone swapped out bulbs in their Superb/Octavia?