TBH you would probably be fine with Eibach Springs on std shocks, they are not jarringly stiff normally, as eibach design them for compliance as well as performance.
For example, when i fitted eibach springs on my Mini Cooper S Works, i found that the suspension was NOTICABLY less stiff, all the crashing was gone and the nasty jarring disappeared too.
Just a thought for you to think about, maybe try a ride in a Z with them fitted?
I am having a set put on wednesday, so i can happily post uop comparisons to std after that.