I have been running 400w hamilton 14k's for about 2 years now, these are great bulbs but I want to go a little bit more blue. I am looking at the xm 15k and 20 k. Wondering if anyone has any good/bad experience with these bulbs and will I see much of a difference with the 15k or should I go with the 20. They will be run off of a m59 ballast.