Purchase an aftermarket rear sway bar to improve body roll while cornering. An aftermarket strut tower bar works well with the rear sway bar as well --- so you may want to consider this as well.
Just keep in mind that even with the suspension upgrades I mentioned. The coupe will still drive like a pig as it simply wasn't tuned to be a sporty handling car. The rear sway bar, and front strut bar will make the car drive significantly more stable in a straight line at high speeds.
