Thiel speakers are very good. I have never hear Vandersteens, but I did own a pair of Magnepans for many years. After I heard the Thiel 2 2 I gave away my Maggies. The Maggies had a huge (dare I say unnaturally huge) soundstage - Leonard Cohen sounded like a huge mouth on the front wall. Maggies have "no" low bass. You can maybe live with that, but the most problematic aspect is the back-radiation (they are bipolar). This can muddy up the sound if you do not position them carefully - which could mean well into the room - which may not be possible. Martin-Logans are also dipolar. I refer you to Wes Phillips review in Stereophile a couple of months back where he found that a pair of MLs sounded best with a wall of acoustic absorbers behind them. These results may be extendable to Maggies. If I had to buy without auditioning I'd go with the Thiels - the 2.3s look interesting.
VANDERSTEENS vs. THIELS
Dear audiophiles, I'm getting ready to buy some new speakers after 25 years of using AR10pi's. I've narrowed my choices to Vandersteen's 2Ce, Thiels 2.3, magneplanar 1.6. Please give me your thoughts on reliability, accuracy, other comments. I will power them with Onkyo m-504 amp (150w/ch) and use rega phono and cartridge,some CD's on a Denon 370. Thanking you in advance hififile, (aka: Bennett).