Of course, since he wants to fill his ZG flares, he'll need spacers with those 0 offset wheels. Big-phil is running sportmax 002's (16x8, 0 offset) and bought 1.5" spacers on all four corners to fill his ZG flares, if I remember correctly. I'll probably be doing the same with 16x8" XXR 513's in the near future to fill out my flares. Unfortunately, none of these wheels come in sizes higher than 16", methinks, even Watanabes.
The closest thing I can think of are Rota RBs, but I forget their offset measurements. I've also heard plenty of bad things about Rotas though, so I'm not touching those with a 10ft pole (says the guy who's looking to buy another cheepo-wheel brand ). Honestly if I were you, I'd go with 16" wheels. There's more choices, and really 17" just seems like too much wheel, not enough rubber for a Z. Look at 240hoke's Z, he's running a staggered set of Watanabe's and they look great. 16x9 -13, 16x9.5 -19 if I remember right. No spacers needed, but he is running coilovers.
But for Wats, you're looking at dropping around to 2.5-3 grand when all is said and done. Something I WISH I could do!!