5k.i got some 6k on mine and i think next time id go abit lower.dont get me wrong 6k are more than upto the job but just abit to bluey 4me.
Luke
From memory, I think that the higher you creep up the 'kelvins', the less light that the bulb projects? I would recommened 5000k, it's a pure white light where as 6000k is rather blue and looks after market...may be problem for you with local police if they've had a bad day.
hidsdirect do them mate, thats where I got my 5000k's. Really can't fault them
Just to throw another spanner into the works, H7 or H7R?
H7, the headlamps in the MK1 Leon are an anti-glare unit so your beam will be nice and focussed.
whats the difference between H7 and H7R?
I'm not so sure mate, I trial fitted a friends H7 bulbs after I installed my own kit and the beam seemed very hairy compared with my H7Rs
Here's mine
http://www.hids-direct.co.uk/supervision-50w-single-beam-hid-kits-p-283.html
Strange, mine are completely fine and passed the MOT just fine