I have a 4 post unit by American Automotive Equipment.
In pricing the total cost, consider up front how you will use it. If it's purely for maintenance of one car, you can get by with your garage door as is. However, if you plan to use it for storage and want the door to clear the top car, you'll have to change the radius of your garage door opener and add a section so it moves closer to the ceiling; unless you have a RV sized door to start with.
Also, if you want to be able to raise it to it's maximum height (in case you want to park something else underneath other than another Porsche), you'll also want to remove the overhead door opener and replace it with a wall mounted LiftMaster.
I ended up making both these modifications over time. Actually, the sequence went like this:
1) garage door radius modification
2) purchase and installed 4 post lift
3) bought a 993 (yea room for another Porsche)
4) added the Liftmaster door opener
This photo was taken between steps 3 and 4 so you can see there wasn't much space between the top car and the door opener. The Liftmaster freed up several more inches above the car. You can see the panel I added to the top of the garage door along with the bigger radius on the track so it would clear the top car.
P.S. The SUV ride height on the 993 is now gone; replaced with a ROW M030 setup.
