Thiel Owners

As a previous Thiel CS 2 2 owner and still a fan to this day, I agree with Jafant.  Good luck!

Oblgny, the 2.4's will be smoother, more refined in the upper midrange/treble, the 3.5's are more coherent throughout, have deeper bass and is much easier to drive.
http://www.stereophile.com/content/thiel-cs24-loudspeaker-measurements#koJxkckLClGEdits.97
Many, if not most would choose the 2.4's, I much prefer the sealed box 3.5's.

Thanks! for sharing- unsound.

I was waiting to hear what unsound would say...  

For me, going from the CS2 to the CS2.4 was a no-brainer. There was enough bass extension and tightness to make the jump. 

The 3.5 (or 3.6) is tricker because of their aforementioned attributes.  I'm not convinced I'd hear the difference at the top end, so it'd come down to the aesthetics of the slimmer design, smaller footprint, and refined craftsmanship.  

Oh, and having the cable connections at the back, instead of the bottom!