Thierry,
I have priced suspension systems for the car. Unfortunately, with the payments and high insurance right now, it's not in my budget. I work with air systems every day, being a designer at a Highway Trailer Manufacturing Facility. I'm sure I could purchase a kit and install it at work. I put $5,000.00 worth of accessories on the car this past summer such as:
Complete stereo install including two 10" subs behind the rear seats and an amp in the back. I had a complete Pioneer system in at the first of the summer. The Amp sucked so I swaped it for a Rockford Fosgate 1300 and added a capacitor. It works sweet!
I also had a little mishap with a toilet on the highway. It fell off a truck during June sometime. A girl that was passing me on a hill, hit it and threw it all over my car. I really got crapped on! Cost me $2200.00 damage to the paint over the whole car. I added the two white stripes (painted on) and cleared the whole top, front and rear of the car. What a difference the stripes made.
K & N air filter
Full professional tint job. Sides were done, got ticket to prove it

I also added a set of 245/45ZR17 Kumo Escta tires. They handle well and stick good. Not sure how they wear yet, haven't had them long enough. Of course the rear ones aren't as good as the front.
This summer, I'm concentrating on mechanical parts. Exhaust system, new UPR shifter. I got a set of BBK Underdrive pulleys for Christmas. Looking into Lambo door hinges too.