i had the PIAA Xtreme white plus bulbs on my R6 (rated at 4000k... model #17655) and they both burnt out within 4 months and i couldnt justify spending another $70 or so if they are only gonna last that long.
i now have the Sylvania Silverstars which are also rated at 4000k, but the PIAA's were a little bit brighter. the stock bulbs are decent but are kinda yellow compared to a better bulb like the other two. if money isnt an issue for ya... then the PIAA's would be the obvious choice... but the silverstars arent shabby by any means either.
2007 Yamaha FZ1, 2007 Husqvarna SMR510
SOLD: 2004, 2003, 2000 R6's