Eibach are the only company in the world to buy springs off ... they are on all Ferrari's, most Formula One cars, all Rally Cars, most Touring Cars etc etc...
Increasing the diameter of your wheels wouldn't normally alter the ride height of the car as you would, normally, fit lower profile tyres aswell to balance the circumference ie.so that your trip computer/speedo still reads accurately.
Note that I like harsh suspension, but I wouldn't fancy anything much harder than my standard TDi Sport on 17" rims (hence low profile ie.stiff sidewalled) tyres.
Ricardo