I've tried both 7500K and 8500K GP Thunders and I couldn't tell the difference, they are very similar and a close match to the standard xenons so you don't really need to change those too.
Why bother changing the fog lights? They should only be used in poor visibility. I did change mine as I already had the H11 bulbs but I never use them as its rarely that foggy.
Current - 2014 F31 335d M-Sport xDrive
Previous - 2012 F31 330d M-Sport sDrive, 2011 F11 530d SE, 2010 E70 X5 3.0d M-Sport, 2007 E92 335d M-Sport, 2005 E60 520d SE