Xdrive and RWD with sport have different stock ride heights. The Xdrive sits much higher.
I have yet to hear of a satisfied Xdrive owner who lowered with springs. They all revert to the original oem suspension or invest in coilovers. The Xdrive suspension set-up is just different, so research carefully before doing anything.
I recently drove a 535Xi Touring with KW V3 coilovers. Just amazing. It was lowered 1 inch. Huge improvement all the way around.
Audio: Jehnert Flatline speakers, Mobridge M1000 DA2 prepro, Helix P-DSP, Zapco Z-150.6 amp
Performance: Cobb Pro Tune, AR Downpipes, ER FMIC/CP, DCI, RB turbos, KW V2 coilovers, Fuel-It Stage 2 w Ported fuel rail, Mfactory LSD