I'm on Sachs - love them... pricey though. If I had to do it again I would have no hesitation in using the BCs.
Regardless of brand, coilovers are one of the best mods to do to any E8X or E9X platform and given the quality range of BCs on offer, it's now very affordable.
The KWs are a great coilover, don't get me wrong, made in Germany quality and all that engineering behind them and if you have the money then you'll love them.
To newbies my recommended mod list is:
2. Exterior stuff like grilles/lip
4. Wheels and other stuff...