If you do some research you will find that the performance with lowering springs and stock shocks will worsen the lower you go. The ride height on the car in the link was achieved with coil-overs and I would bet that the ride quality will suck if you tried to go that low with the spring-over kit. Even with coilovers that ride-height is very impractical. I had mine set almost that low and I was scraping often. It looks cool but it takes away from the driving experience.
'13 SSII M3 Coupe - KW Clubsport 3-way (Eibach Front Spring Conversion), Akrapovic Evolution, ESS Tune, StopTech Trophy, IND Euro Front Bumper and Gloss Black Mirror Covers, TMS Studs/Lugs, BMW Performance Carbon Fiber Spoiler/Interior Trim/Center Console, BMW Edition Grills/Gills, BMWPedals Extended DCT Paddles, Mode Carbon GT4 Splitter, Advan TC3 (18x9.5/10.5), BBS E05 (18x10/11), G-Force Rivals (275/35/18, 295/35/18)