Thiel CS2

Do a search here for the Thiel owners thread, lots of helpful folks there.  I almost pulled the trigger on those speakers back in the mid-80s, but got CS3s instead because of the additional bass (and I couldn't afford the 3.5s at the time).  The CS2s won't go much below 40 Hz, but they image beautifully and are very coherent speakers.  In a mid-size room they will sound very good.  I have heard them with NAD amplification and more expensive amplification, they will benefit from better sources, but they can sound good without them as well.

Type in "thiel owners" in the search box for the forums and you'll find jafant's thread that started in 2016.  It has become a good thread for Thiel owners to converse and share knowledge about the speakers and associated equipment that works well with them.

dlcockrum is right.  In the 80s, the differences could have been described as the Thiel sound was tilted to the higher frequencies (Jim Thiel argued that the response was flat), the Vandersteen as a darker sound.  I think the two brands evolved so that they are closer in their tonal presentation now, but each has its own sound that you may or may not prefer.