I just replaced my S60 and XC 70 suspension
Groton has what they call a quick set , springs shock mounting plates comes all put together
just plug and play

First, inspect the Nivomats for leakage at the bottom of the piston. To test:

measure the distance from the ground to the bumper. Place a very heavy weight in the rear, like your neighbor holding a 12 pack of beer? Push down several times letting the back of the wagon pump up and down. Then measure again. The distance from the ground should be close to the original measurement.

Or drive around the block with the weight in the back. That will also 'pump' up the Nivomats.

On my 1998, I had one die. Easy to replace, but the cost was a LOT. I wound up at a junk yard and bought a pair.

If your car rattles a lot from the rear, consider changing out anything that has a rubber bushing.

Front shocks, I went with Koni Sport $$$, but original springs. HD parts.
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Keeping it running is better than buying new

I suggest telling us what suspension parts you've replaced already. We can then go from there...James Souza is correct. Only replace what you need.

If the front struts and spring seats have never been replaced, that along with tie rods, control arm/ball joints would be at the top of my list! Please give us the car's suspension/steering parts replacement history if you know it.

The only motor mounts that might need replacing are the upper torque and the lower front near the passenger wheel. They are both rubber. I've replaced both on my 850's. The other mounts are hydraulic. You should check them but they are most likely okay.

Upon further review ... You should take a good look at your brake hoses and rear calipers - these items and the rusted rear suspension adjustment (the car ate right rear tires!) led to my trading the car in on a '08 XC70.

Two years ago, my car was just about like yours

Isabel (our'96 855R) was the best car I have ever owned - I miss her!

To check the suspension, I would have a good alignment shop look at it - my shop does work for local indies, and they are great.

Or have a dealer check it out - mine is not bashful about telling me about things that might need work. Why replace things that are in good shape?

I had a '96 855R (Isabel) and I found that the space between the tires and wheel wells would vary if the car sat for a couple of days - I suspected that the nivomats sank a bit.

However, as soon as I drove a half mile of so, and went over a couple of bumps, the clearance corrected itself. Once I picked up a B16 with transmission - the rear dropped 2 inches, but came up level after a mile or so!

I surmised that the nivomats were OK.