2-channel listening with a sub-woofer

As usual, small diameter drivers are said to be "faster".
Frankly I have never heard a "fast" 16 foot organ pipe. I think that what we really mean is that the cone is under tight control of the power amp, and this depends on the power of the driver "motor" and the mass of the cone rather than the diameter of the cone. If you have an 8 inch driver and a 10 inch driver from the same manufacturer's line, and they both have identical voice coils and magnets it is reasonable to assume that the 8 inch will give "tighter" sound. But if you compare a typical 12 inch driver with a 2" voice coil against a 15 inch driver with a 4" voice coil and twenty-odd pounds of magnet one cannot make assumptions. Throw in servo control, and all bets are off.

I use Martin Logan CLS 11Z and a depth sub. Three 8 inch drivers made by the same company that made the main speakers in a non HT set up in a very large room.
Try to stick to the same company for your mains and sub.Saves a lot of trial and error and mismatching, but not 100% fool proof. That's where your ears come in.

using the new tact 2.2 rcs with two subs seems like an interesting idea

I get seamless integration, but the sub and speakers are from the same company.

"have you ever heard a subwoofer for 2 channel listening" sorry but that sounds funny... people have been using subwoofers with stereo systems for 30 years or more... Dalquist, Velodyne, Janus, JBL (and others) all had subwoofer products in the 70's. The famous Beverage speakers came with a pair of subwoofers.