I have Tein type flex (not the street ones) fully adjustable for bump/rebound/height etc they work great on the track, they are a little stiff but you would expect that! Think I paid £1600 odd for them.
Still compliant enough to use on the road. (you know what they are like on track from the passenger seat
)
They are still going strong after nearly 4 years and 35k + miles I'm sure they will need a rebuild at some point though, they have already outlasted a set of standard shocks and springs!