Thank you for the feedback. All things considered, it would appear that going one size up and getting the PSS's is the best option. Given the popularity of this setup, I gather no one has had any issues getting their cars serviced under the BMW warranty? I've heard talk of rubbing, ABS not working, speedometer and odometer not reading properly...etc. I take these grumblings lightly but everything needs to be considered.
Also I have been told that the PSS's are quite soft and might not last very long for normal driving, which would be a shame as they are so expensive. What kind of mileage are 1-series owners getting with these?