piaa =sucks donkey ass......
i had the super plasma gt-x bulbs when i had my stock housing.......what a dissapointment. the bulbs were so damn pink, i flamed down the streets every night, not to mention that the light output was so much more less than the stocks.
silverstars i havent used, but i've seen on SRT-4s around here. For the most part they are pretty white, but they also look like they lower visibilty as well.
MTEC- i've heard alot of good about them, and they are currently the competition w/ the silverstars. According to what i've seen, MTECs are more based on color output than light output.
So u might have to ask around to get more info on the other bulbs...........but don't ever go w/ PIAA