I got wheels + tires + shipping for under $400. You should be able to find a set of those wheels dirt cheap without tires. they have the same bolt pattern and are +45 offset. I think they are an 8" wide wheel but could be 7.5.

 

I would say take your car to an HPDE or an autoX and see what it can do. then modify it, suspension doesnt have to be stiff to handle welll

 

If your not going to use it on the track... Why modify it?

Oh ja, it would look cool.

 

Hmm...same question as why I modified my sentra...and made it look stock. It's not for looks, why would I slam a car?

Track racing and track times arn't the only things that matter when it comes to modifying a car.

Small things can help improve the drive. I believe going to a coil over suspension would be more beneficial. Why? because the coilovers solve these issues.
#1) The RX8 to me has too much body roll, even on the street I don't like how body roll feels.
#2) The ride although is good, I feel it's a little too soft for my liking.
#3) Shock and spring combos either lower more than I'd want it to be lowered, or don't provide a high enough spring rate IMO to negate body roll enough.

People have different reasons for modifying cars, I for one cannot stand most body kits and showy type stuff, because more often than not they make the car heavier, much too low, and I bought my car to drive it, not to park it and win trophys.