After much questioning and reading, I've decided to go ahead with what I think is the most important upgrade for the Turbo, IMHO more important than wheels/exhaust/power: Bilstein PSS10 Damptronics. My rambling will follow and any suspension expert or professional please chime in and correct me as needed. This is a hopelessly complicated issue and I could only hope to be "near accurate" with my web based research .

While I have felt that the Turbo's stock suspension is too soft *for me* (and apparently a number of other drivers, and some trustworthy reviewers of magazines big and small--I hope someone at PAG is reading this), resulting in too much leaning/rolling in corners and squatting under full throttle, a recent test drive in the GT2 hastened this process. The goal is not to turn my Turbo into a GT3/GT2--that will be the job of my second Porsche, the next gen. GT3 with no RMS leak, PDK, PSM, and more power , but definitely to take it in that direction while maintaining the Turbo's incomparable daily-drive ability.

It came down to GMG Spring vs. Bilstein. The GMG spring is progressive, meaning initial response is soft, then the spring becomes stiff as it compresses more. While people's opinions vary, I've found that progressive spring is not necessarily the best solution. In addition, I don't think I would like this type of behavior, the initial softness of it. (Google "linear progressive spring" and read on your own if you are interested.)
In contrast, the Bilstein is a stacked springs (linear main spring + tender tender) setup, AFAIK a more advanced, costly, and desirable solution.

In addition I am hoping that the PSS10 damper would improve upon the stock damper. My impression of the stock damper is that Normal is too soft, and Firm has poor bump management, causing the rear wheel to lose contact with the road when there are bumps at high speed. Mid corner high speed bumps literally cause the rear to walk/shift sideway.

In other words by firming the damper to reduce pitch/roll in corners (slow response), the stock PASM system I think somehow has sacrificed bump management (fast response) and causes poor behavior unless road is glass smooth. I am hoping the PSS10 damper will do this better. (BTW, the GT2 Normal setting is firm but doesn't feel anything like the jittery and choppy character of the Turbo's Firm. I don't know why & how, but the 2 are very different from each other, decidedly in favor of the GT2 IMHO, based on my test drive.)

Lowering: IMO, the law of physics implies this alone might be one of the most significant contribution to improved handling, besides stiffening. Lower is better, and since the cost is only $150 , I am going to drop the car 1 inch and see how it affects me in daily driving. This is another area where the Bilstein has clear advantage over the GMG Spring: ride height is adjustable.

Anyway, enough of the rambling, here's what showed up at my doorstep today.