No experience with Doug's package for the Z06, but am familiar with his background, and he knows how to make horsepower in a Vet, PLUS handle well! There are a large number of aftermarket suppliers/manufacturers out there, but Rippie has the experience and skill to do it right!
Good luck on your Z....I'm sure others will have the answer to your specific question.
Mr. hide, the DRM 40 hp package was tested using my car last fall. I would suggest DRM long tubes which are part of that package, a Donaldson Blackwing, and the exhaust system of your choice. I personally would stay away from PRTs. Not loud enough at wot and too loud on cruise. Just mho. The DRM long tubes on my '01 gained 19 rwhp and 19 rwt. The Donaldson Blackwing will account for most of the other gain. Mufflers will give a few: probably 3 to 7 rwhp. The total gain on an '01 should be the 40 DRM claims. It was on my car. If you call them ask for Peter or Tim.