As said, it's always best to get matched springs and shocks and even more so when you're wanting to go 40-50mm lower.
With suspension you get what you pay for so if you can afford to push for that little bit more it is worth doing so.
The Weitec Hicon GT coilovers were brought up and for the money they really are an amazing kit and especially with nearly £100 off them until the end of August.
Damian @ DPM Performance