You have an auto right? If you have an auto I think you will get beat. My grandma has one and I drive it quite a bit. It is pretty fast. My mom has a buick regal LS which has the same 3800 Series II engine and it could probably come close to keeping up with my 5-speed. In my mom's regal i pulled on a 5 speed Sebring with I/E. It might be close though. My moms car has 200 hp and I would guess the Impala has the same.
I don't know I was just looking in a article of MT yesterday about the Monte Carlo SS and the Impala SS coming back with Supercharged V-6 engines instead of V-8........ At least for now. (I'd still rather have a 96 Impala).
On www.chevrolet.com it tells about chevy's new line of SS vehicles. The Impala SS and the Monte Carlo SS will come with the Supercharged 3800 Series II engines the same used in the Grand Prix GTP and the Regal GS putting out 240 hp. The base models of these cars have the regular 3800 Series II with only 200 hp. My moms Regal and my grandmas Impala are pretty quick off the line. I think it will be a pretty tough race for you. Good luck though.
SE-175 hp (3.1L) TQ-195
GT-200 hp (3.8L) TQ-225
GTP-240 hp (3.8L SC) TQ-280
180 hp (3.4L)
2004 SS-240 hp (3.8L SC)
My best friend has a maroon Impala LS Auto (round taillights). I've been in that car when he raced an auto Cavalier Z23 and lost to it by a car length. His other car, a 2003 Monte Carlo SS, on the other hand, is very torqey and will kill a 6spd GT-S off the line. I'm not too sure how the overall outcome of a race between a GT-S 6spd and a Monte SS would be though. As for the Impala, Depending on the type of engine it has, you could win or loose but I don't know very much about those cars.
EDIT: Nevermind, I don't think my friend's Impala is the LS model. Probly something lower.