The Performance springs won't lower the car that much. I think cvc is on the money with the spring recommendation since you already have the Performance dampers. The stiffer springs will do more for your handling than the sways by a long shot; sways will help only in turns. Rule of thumb when upgrading a suspension is to address the main issue first and not work around it. Sways count as the latter, aka a band aid for the too-soft stock spring rates.
2011 BMW 335i E92 - Le Mans Blue, 6MT, M Sport. JRZ RS Pro, Quaife LSD, BMW Perf Exhaust