So I finally found a dealer that has both the 4.8i and 3.0SI I could test drive. I think the 3.0SI has enough power for me. The 4.8i was nice, but I actually felt the 3.0SI had a smoother start from a complete stop. The 4.8i I drove tended to torque out then jerk forward then it would accelerate. On the freeway, they performed similar, so I think the 3.0SI with the sport package is the one I want. Now to just get rid of the GMC Denali and find the one I want.