Putting a system in a 02' SS

Am thinking about buying an SS or a firebird. Wanna put a system in the back, but am afraid that the 80lbs of extra weight would make the car considerably slower, and even more barge like. Also, am not even sure that the SS/bird needs double 12's. Any advice? Could i get by with like a single 12, or maybe even a 10? And dont say, F%$k the system and spend the money on mods!

I have 2 10s in my 95. Sounds great, looks good, and can always use more bass! I suppose it was faster without the extra weight, but I've had them for like 3 years now, and the difference is negligable. I MIGHT have noticed it at first, but honestly don't think I did. It's not that serious. I say go for it! One twelve would be enough for most people, especially if it's the right 12, but like I said I have 2 10s and wish I would have gotten two 12s instead! Also, do you have ttops? I don't so I can use the storage area for my subs. If you have ttops, you have to take that into consideration...