Depending on how old your bushes and top mounts are you could replace them. Even fitting new standard parts will give a better feel if the existing parts are old and worn.
You could opt for poly bushes.
I have a front gti arb an that made a difference.
I don't know how much the chassis flexes so can't comment on the benefit that braces may have.
If you haven't I'd take a good look at the brakes, pads, discs, drum, piston seals. Stopping in time is never overrated.