I just posted
an article on balancing a 911 from 1992. This was exotic stuff back in 1992. Now it seems that everyone has a set of scales.
I would say though of all the things I've done to my 911 over the years the scales, and the weight balancing, made the biggest difference in how well the car handled. You can buy all the trick parts you want but balancing the car out - and properly aligning it will be the most cost effective thing you can do.
Richard Newton
The Complete Trailer Handbook