I removed the mid-muffler and the two resonators, added an X-pipe and installed Flowmaster series 4400 axlebacks.
I absolutely love the sound...deep and throaty. When I first installed them it was a little raspy but after the new pipes carbon'ed over the deep throaty sound emerged.
There is drone but minimal. This is my daily driver in the summer. The drone is only when your on the gas, when your cruising or at idle there is virtually no drone.
Absolutely no regrets. I was afraid it would be a ricer sound but I was pleasantly surprised at the deep tones.
No noticeable power gain.
Also I have the K&N CAI.
2008 G8 V6: Eibach lowering springs, 18" staggered rims, K&N CAI, Series 4400 Flow Master axle backs with FlowMaster tips, radiator cover, tinted tails, silhouette of G8 third brake light.