Speak to AMS about all those things. They can usually get you deals on everything if you buy it as a package and sometimes deals on their own parts. http://www.amszstore.com
I’m sure they will set you up well.
As for the Stillen Sway Bar kit, I wouldn’t say it’s necessary. I’m sure people would disagree. I’ve driven 300s with, and without and there is no significant difference with the sways kits. The best upgrade for sways you can do is if you have a 2seater, get the rear sway bar off of any 2+2 car. It is a bit bigger on the 2+2 than any of the 2seaters, whether NA or TT. On a lot of road courses, you rarely hear of the 300 drivers upgrading the stock sways on their cars.
Seems that most people disagree here with the next thing, but I felt a pretty significant difference in my car when I put on the Strut Tower Braces, both front and back. When I put on the back, I could go into and come out of corners faster without the back sliding out. When I put on the fronts it removed the tenancy for the car to “track” on road grooves and made the car more responsive to sharp turns. I would definitely add strut tower braces to that list.
Energy suspension Urethane bushings all around get rid of the sloppy feel to the car, and axle hop during wheel spin is eliminated if you put on solid bushings on the rear subframe. Beware of those though. They can do some damage to the frame of your car if you drive over big potholes and bad terrain. If it’s my car I would just put on Urethane Bushings for dual duty, both track and street driving.
It’s not necessarily suspension, but I would jump at the opportunity to put on Urethane bushings on the steering rack. Bernie at tt.net sells them with a high grade long bolt to ease installation. It was night and day for me in how the steering felt. Before the upgrade I’d watch all my turns very closely, both hands on the wheel and I’d constantly have to adjust based on the road surfaces. After I did the upgrade I could hang a turn with one pinky finger on the wheel and know it was going the same place every time. Ask AMS if they can get it for you with the long bolt as well. I know they can get you the Energy Suspension Bushing, but I’m not sure about the long bolt. There’s really nothing special about the bolt. It’s available at Brafasco, but I don’t remember the sizes.