Just wanted to add my tuppence worth on this, but I'm very happy with my Leda suspension. I have the rear helper springs and yes, there is a little noise occasionaly (easily drowned out by engine noise [
]), but its not intrusive and no worse than any other mechanical noise in the car, so easily ignored.
The transformation to the handling on the track and road is fantastic, I have them set about mid way which feels very taught (which does make you want to drive around pot holes) but its still quite comfortable and I don't often feel the need to change it for trackdays. I think we used 300lb/ft at the front and 100 at the rear, but having experienced it with and without the M030 roll bars know that they are mostly responsible for the firmness.
I can't remember exactly the cost of mine but it was circa £1K in a group buy as Fen mentioned (which was just after a price rise).
If I were in the market again I would definately consider the KW's - I particulalry like the idea of the valve that takes the impact out of bumps/kerbs, but wouldn't have any hesitancy about choosing Leda again (and they're fairly local so I know that getting them serviced should be pretty straight forward).
In fact the only thing I want to do with the suspension at the moment is lower the car further, but that's quite a long way down my list of priorities at the moment.
Best regards,
Peter.