If you are going to get enough use out of adjustable damping and so on, then an expensive set like KW Variant 2s would be a good idea. If it's just to get low then Hot tuning/Jamex/etc work just fine. If you go for something like Spax RSX coilovers or Weitec coilovers (I think they're called Weitec GT?) you won't go as low, but your ride will be better and the damping, even if it's a set 30% or whatever, is much better sorted than on cheaper coilovers. You would notice the difference when cornering hard.
It's worth noting that no matter what brand you get the ride gets a LOT harsher if you have them wound down to the very bottom.