I also did the impact bushing, z1 urethane transmission and z1 solid motor mounts. The car is rock solid and if you are sensitive to noise I would not do the sub frame bushings as they will make some noise during deceleration more so than all the other upgrades. I don't mind it at cause it sound like a race car lol. You will also get a whine from upgrading to a solid diff diff bushing too. And you may get some cracking and popping from the SPL upper arms and impact bushing too...just get them greased the best you can. Mine creek when making slow hard turns like backing out of my driveway! I think that sums it up pretty well.
