BMW intended for those dampers to be used with oe sport susp springs, so that's my recommendation. I just happen to have mine available f/s
but our cars are different so maybe that's not ideal. Lot's of folks are happy with Eibach p/k springs with those dampers, but get shorter bump stops if you go that route. Another viable option is BMWPS springs, but again you'd want to get the new PS bump stops to go with those springs.
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