Here's a RSB (rear sway bar)
Here's a tread how to install with another pic
http://www.solaraguy.org/viewtopic.php?t=33312&highlight=rsb
I agree, this is your best bang for the buck performance mod.
If you can lower it (with Eibach springs and Tokico struts), your handling will be far superior than stock. You'll lose that floaty feeling

This is an Injen
Short
Ram
Intake (just the blue pipe) with the
Cold
Air
Extension (just the chrome pipe that goes into the wheel well).
There's also a
Cold
Air
Intake, but unfortunately no company makes one for our car, basically the same but usually 1 piece. Since nobody make a CAI for our cars, we use an extension. The CAI/CAE is great because the filter doesn't sit in the engine bay sucking in all the heat from the engine.

I would do those mentioned above, plus the tint and definately an exhaust/muffler. But, the exhaust/muffler is something that you'll have to decide on. There are some cat-back (after the catalytic converter) made specifically for our car, but you'll definately pay some bucks for it.