IMHO the Venaci Spirits and Mesh rims are very good looking on the Z. I'd also consider the Volk TE37's in black. There are many pics of these rims, just do a search on this forum. As far as spokes, i feel that 6 or 7 spokes look best for the Z.
Edit
ok, so i dug up some pics:
Venaci MESH:
Venaci Spirits (yes, same car as above):
Volk TE37's: