Bill - I evaluated and graded the models in context of my XO upgrade project. For starters, all the products are worthy; each was Thiel's best work at any point in time. However, some were more successful or more fully realized than others. In general, the more recent products are better due to continual learning. I have chosen models that were technical and market winners. Generally, they are the most recent of each series-type. The technologies constantly evolved, plus more recent products usually have larger quantities and better spare parts availability. All that said, your biggest liability with low-count / older products is driver availability for repair. Check with Rob at CSS regarding driver availability before buying anything.
The 5, 6 and 7 series remain hypothetical in the upgrade project. The 5 has some interest, but
huge upgrade issues and small numbers. No interest expressed in the 6 or
7.2. The XO project is in its infancy, so we don't know what will
develop.
The x.7 series are most recent and parts are available; not many were sold. Best of form and possibly collectable.
In the 3- series, the model 3.6 was an all-time high seller with mature
technologies. The 3.5 has a strong following, but the drivers are no
longer available, so beware. Also, although the equalized bass is
sealed-box / low-order and natural sounding, its single driver configuration
restricts its output. So a modest room and listening levels are
required.
In the 2- series, the 2.4 is the darling. The 2.3 can be found cheap for
reasons including transitional technology. The 2.4 coax driver eclipsed
the performance and reliability of the 2.3 coax. The 2.4 is our first
upgrade hot-rod XO due to its larger numbers and greater finesse.
I am also addressing the 2.2 as a personal favorite of mine, and I have the final prototype pair.
In the 1- series, I have chosen the model 1.6 as the most mature of the series: best drivers, highest count, etc. Earlier 1.xs will work well and can often be found for pretty short money.
I am also addressing the PowerPoint 1.2 as a stunningly effective product with room to upgrade. Its niche was home theater, but I use it as studio monitors. Again, due to my personal appreciation and interest.
Similarly, I have the 02 final prototype pair and will upgrade it.
As a company, Thiel applied the same design goals to every product. The personality of each model is unchanged through its generations. We were definitely product / performance driven rather than market-responsive. Such an approach is unusual; it gives you, the user access to any and all models having essentially the same objectives, albeit with varying levels of success. Welcome to the journey.