C4S M030 shocks with standard springs?

I need to replace my rear shocks as they're done and its close to the same price for me to buy an entire set of (4) M030 shocks vs just the rear pair of stock shocks. Weird I know but that seems to be the case. I realize that there will be a difference in ride quality, but I'm just wondering if this is ok. My garage says its ok but just want to make sure there wont be any other adverse effects? Hoping if anything it improves the handling?

I don't know your local market, but I'm surprised that Porsche OEM 030 shocks/struts would be half the price of Konis or Bilsteins. I also would be reluctant to mix standard springs with shocks designed for a different application. Hopefully someone else here has specific experience. The parts will no doubt fit and work. If they are close to Bilstein B6s and will work with a standard spring length, you're good. But I think 030 package is lowered, so they may be designed for a shorter spring length, similar to Bilstein B8s. My '04 C2 has stock springs and very recent B4s. With the addition of Eibach sway bars, its handling is excellent, but it may get B6s in the future.

The Bilstein M030 rear dampers are extremely firm, they are 15% firmer than the EU M030 dampers. I put some on recently, my car is a UK M030 C4, and the ride was horrible. They lasted a few weeks and had to go. I tried with standard, non m030 springs, and there was no difference, just sat higher. In the end I just bought some used Porsche dampers that had come off a car that had only done 20k miles when they came off. So much better. Unless you have pool table smooth roads I would not get the Bilstein M030 dampers.

Spend a little more and get a matched set -- springs, shocks, bump stops. what you're asking might work, but there will be compromises.

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I'm a stock ride height and 17" holdout and when it was time to replace my rears, since new B4s were on the front, I chose to save some money and just get the same for the rear. I have rough roads here in NC to drive on, so I figured why lower it. But when I was trying to push through various corners I always felt the front end was too understeery. And no wonder, the stock sway bar on an 01 is pretty flimsy, presumably for safety sake. The eibach bars are far more substantial. And my car is now flat and feels balanced through those same corners. ​​​​​​But this brings up a question. How many have lowered their car on coilovers or aftermarket springs and left stock anti sway bars on? If you did upgrade the anti sway bar, how many did it at the same time as coilovers, and how many did it after, and did you feel as much difference as I did. Coilovers and modern damper design must have come a long way since the B4 was introduced. But not enough to overcome noodle like antisway bars.

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I'm on the other end of NC with great mountain roads. My 981 Boxster S has X74 sport suspension and is fantastic, but still comfortable; it's a bit of a fair weather and special use car.. My 996 is very different and my goal is to have a good handling "everyday" car. Not a daily driver, but an all around sporting car. The relatively fresh B4s and stock ride height were a start, but the sway bars were night and day....good adhesion (Michelin PS) and now very little roll and good front/rear balance. For those who have swapped for lowered springs/coilovers, I suspect that the updated damping and lowered center of gravity would help with roll, but I would still think Eibach, H&R, or other sways would be an improvement. Just speculation.

Never underestimate what a sway bar can give. A slight increase can really increase overall stiffness. I have the M030 bars, they are less than 1mm thicker in diameter, but they are more stiff too. They make a big difference.