Matt, what I have found is you can sell your old springs from half to about 2/3's of the new price depending on condition. So It might be better to try J's on the rear and use your spacers on the front. Then sell yourold springs to recoop most of the costs.
I did the springs and then did J shocks and bump stops later. It's not all or nothing, you can build up your setup and upgrade as you go.
Ken Romer - K0ROM
02 Kimberley Kamper
09 BMW Z4 sDrive30i