^ +1 above. depends what you want them to do for you. if you want just to go low, actually perform or perform well for track purposes.
there really are dozens of coil-over threads in just the last month. Search and you'll see what people have said about different brands.
OE CSL WHEELS - OE CSL BRAKES - OE AUTOFLD MIRRORS - CSL TRUNK - CSL DIFFUSER - AA TUNE - AA PULLEYS - AS 40% SSK - BILSTEIN PSS9s
CF CSL LIP - NAVI - BMWPERF CF STRUT BAR - BMW GROUP N MNTS - GRUPPE M CF INTAKE - SUPERSPRINT - UUC BRKLINES, TRANS, RTABs - H&R SWAYS - 4.10 M-SPORT DIFF