I have Silverstar's -4000k. According to the back of the box, I guess it is the brightest before you go into the HID's. ?
I tried 4 different blubs including Silverstars (A friend had an 880) none of them came remotely close to matching my 6k HIDs. My solution? Get 880 6K HIDs too, problem solved...
I wouldn't waste money on finding a matching blub, theres a good chance you won't find one. I had blubs that were all blue and they still looked yellow compared to the HIDs...