Roadracer,
I suggest you pick up a spare rim. Tire Rack is notorious for not keeping stock long. My buddy had to dump three six month old rims he bought from Tire Rack when one on his XR3 cracked. Same thing, licensed by BBS.
They sell replica Porsche and BMW wheels too. I have blizzaks on replica M3 rims tire rack sells. The Porsche rims are mile miglia, and weigh about 30% more than a stock rim and are not as durable as stock porsche rims. with 350hp vs 208 on my Porsche I wasnt as concerned with a few extra pounds of unsprung weight.
Also, If you lower the car, the shocks will have more of an effect on ride than the springs. My Z28 had SLP SS Stage II springs and revalved Konis. with 17s it was too stiff. with 16s it was stiff, but bearable. I almost sent the shocks back to Koni in CA to have them revalved.
Edit: i mean bilsteins. the konis were on the porsche. whoops.