My Thiel resume is a lengthy one, as follows :)
1)Auditioned the 2 2s at a dealer (w/ BAT electronics, MIT cabling, Naim CDP, jazz music)
2)Owned the 1.5s for a year
3)Traded up to the 2.3s and have been using them for the last two years.
Wish I had a clear favorite among them, but I don't. Whenever I see someone selling the 2 2s for 1K - 1.5 K on the used market, however, I regret not having an extra room in my house for a pair. They are that good. In terms of value for the money, used 2 2s represent (to my mind) one of the best deals on the market.
I have the 2.3s now and like them for their excellent precision and the somewhat greater "presence" they offer over the 1.5s I owned previously, if not much of a boost in the bass dept.
I don't think the 2.3s give you a tremendous improvement over the 2 2s.... maybe a bit more detail, transparency, and bass tightness.
But here's the deal with Thiel: They are very accurate loudspeakers. They will "notice" when you change speaker cables, interconnects, move them too close to a wall, etc.
That applies to any of the Thiel models I've heard.
Use a quality source component (Cal Audio, for example) and ample watts to drive their 3-4 ohm load.
If I were choosing between the 2 2s and the 2.3s and I doubted the quality of my source or amplification, I'd opt for the 2 2s, which seemed to be a bit more forgiving.
To give you some context for my comments: For the 2.3s, I use a McCormack .5 Deluxe (Revision A) with Shunyata power cord; this results in a nice refined sound with excellent extension (not bright). The McCormack .5 was plenty of muscle for the 1.5s, but maybe just enough for the 2.3s at normal listening volumes. I suspect that the 2.3s really crave something on the order of 250 watts into 3-4 ohms, so I might be looking at a larger stereo McCormack (or monoblocked .5s) at some point.
Other Thiel owners report good results with Classe and Plinius, but I haven't heard those combinations myself.
Bottom line: If a friend asked me to recommend the best speakers for 1K, I'd tell him or her to try to find a used pair of Thiel 2 2s in excellent condition.
Some other speakers in the price range to consider: Revel M30s, Aerial Acoustic 6s, and B&W N 804s.
Hope that helps...