I’ve never heard the 3.6 so will defer to others other than to say the 3.6 reaches deeper into the lowest octave and appears a more difficult load for the amp. Also, I’m a big fan of the coax in the 2.4. My short list of Thiels I think better than the 2.4 are 3.7 and 7.2, maybe the 6 and 2.7 (haven’t heard the last two). And that’s not considering my crossover upgrade. Don’t think I’d trade my pair for stock 3.7s or 7.2s, certainly not without listening first. Tracy Chapman is in my living room as I type :)