Congrats to all you 3.7 owners! I'm still hanging in there with my 2.2's, which have become more expressive and "alive" since I started powering them with PS Audio M700 monoblocks. My search for new interconnects has also shown me that the 2.2's can take on several different personalities depending on the cables being used with them.
I had been considering trying a REL or Thiel subwoofer with my speakers, but I'm now leaning against that option after appreciating the positive effects of my recent amp upgrade. I already have a Thiel SS1 sub that is blended to five Powerpoint 1.2's via a Thiel 5-channel crossover in my HT system, so I know how well that sub can blend with other speakers. However, I also really value the naturalness of having the 2.2's cover the low frequencies without adding crossovers and dividing up the bass among more drivers. If I did add a sub or two, I would definitely do it via high-level connections (like the REL or Thiel approach). The fact that my 2.2's already have decent bass and I don't listen to music with a lot of content below 30Hz makes a sub less of a necessity for me.