I agree with evil,
As good as my 800 degree project Mu's are on the track, they just don't cut it when dead cold, to be honest, the older they get, the worse the cold performace seems to be. I can't really complain though as they just don't seem to be wearing out (and neither are the pmu rotors) and they have done 5 days at wakefield now and never faded once. The same can't be said of the cheap shit rears.
If you decide to go with a middle of the range pad (and i think your choice of a 550 degree pad is a good compromise), you will need to accept that it won't perform optimally in both situations, so the only way around it is to swap pads continually.....