I performed the upgrade from Thiel 7 to 7.2 myself. It took two of us about 4 hours to change out all of the drivers, crossovers and input connectors. The only thing remaining from the 7 is the cabinet and some of the internal wiring. Without being able to compare them side-by-side, and after a long break-in, I would have to say the 7.2 is better in about every way. Sonically, it is more transparent, detailed and has more articulate bass. It is also a little more efficient and easier to drive, although amplifier matching is still very important (if the amp sounded good with the 7s, it will be great with the 7.2s). Is the change worth $4000? That's a little more difficult to answer. If you sell the 7s used and add $4000 to that, what speakers can you buy that you will like as well as the 7.2s? The answer for me was the upgrade - you'll have to decide for yourself.