spax are real good value for money specially at £100 note, the drop is goo also.
The performace is probally just over adverage but compared with simular brands could probally top them in value for money.
However if you want even better springs you would probably looking at paying around 3x that amount.
better makes to consider:
faulken - top notch.
eibach - probably better then spax but some say are to soft.
IMO go for it