In case you have any questions concerning the chassis/suspension of this car, you can go here:
http://www.4g61t.com
I used to have the turbo version, and even though I had nearly 200hp to the wheels, I could still get 35mpg out of it.
If the weight is going to increase, you can use the front shocks and springs from an eclipse. The spring rates and valving should be suitable for more weight then the stock parts that you have on there now. I don't remember if the rears are interchangeable with the eclipse (FWD model), but I suspect they are since the suspension setups are nearly identical.