I had the 3.5 and got last year the 3.7. I can argue both ways: the mid and highs of the 3.7 are superb, but the bass and extended bass can be improved with subs. They're improvements that shine in a large room. Now, it all depends on the room. If your 3.6 work for your space and more importantly, you have learned to like them for what they are, and all the drivers and xo are good, any change to a 5,6,7 or 3.7 will involve a trade off. Proceed with caution, and clarify your goals depending on your situation. By tailoring my 3.5 by going with tri amping, replacing some drivers and carefully applying dsp, I was able to approach the listening experience of the 3.7 using the 3.5 in the space they were located.