Buy the cheap PI or Apex springs and fit them, then in 2 months when you hate the quality of the ride buy the Eibachs.
Or buy the Eibachs first and never look back, in reality that's saving you £100 and 2 months of misery !
PI are so good they offer this money back guarantee:
Your moneyback guarantee If you are not 100% satisfied and want to return the kit within 30 days of order in unused condition we will refund in full.
So if your not 100% satisfied with how they look in the box then you can return them, fit them and they wont take them back.
Now is that the guarantee a good quality spring company offers ?