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 E92 335i, 6MT, Le Mans blue - Quaife LSD, JRZ RS Pro, JRZ camber plates, Eibach ERS, full M3 susp, custom toe arms, Powergrid end-links, SS brake lines, brake ducting, Michelin PSS, UUC SSK, ETS FMIC, ER CP, Perf. Exhaust, VAC RSIK, Sparcos; work by VAC Motorsports in Philadelphia