I ran fsd's with sport springs for a couple years. Better comfort and handling than the oe dampers. You won't need an alignment or different bumpstops. Sonic MS in mtn view is a great shop. You won't get much if anything for your oe dampers.
2007 E90 335i, TiAg, 6AT, ZPP, ZSP, ZCW, 6FL, HD
Quaife lsd, ETS fmic, GIAC s/w, Dinan intake/exhaust/oc, KW/M3 susp, Apex Arc 8, Mich PSS