How many miles on your car? Klaus is right, the upper mount is the only one that typically goes at <150k. My money is on that one.

Did you take a really good look at the rubber on the upper mount for cracks? The rubber on my 850's upper mount was dried out and cracked which allowed the engine to shake more than it should. Sounds similar to the symptoms you described. I put in the IPD poly and had no problems with it. If you replace any of the other mounts definitely use OEM. The IPD upper mount is an easier install because the factory mount is pressed in. No need to get under the car if this is the only mount you need...:)

I have never heard of the tranny mount going and lower front engine mount usually lasts a long time. Mine is still going at 200k. Here is a description of how to troubleshoot and replace the lower front mount (passenger side) from Volvospeed. It is for 850's and S/V70's through 2000, but I'm guessing your 2001 has the same mount.

http://volvospeed.com/volvo_repairs_how_tos/engine_repairs/front_engine_mount.html