I have owned several Wilson speakers over the years, all but one pair was purchased used. I actually like the 5.1s better than the 6s but not as much as the 7s. Maybe it was the set-up of my system versus the systems I listened to the 6s in.
I do not like the Sophia 1 or 2s as much as the W/P series, but that is a personal preference. I find the Sophia's to be a kindler, gentler Wilson speaker - sort of like taking one 75% of the way into the Wilson House sound, but leaving some "forgiveness" in the speaker. In my opinion, the Sophia is a transitioning speaker to the Wilson house sound in this manner. Don't get me wrong, it/they are very good speakers, but for me that did not deliver enough of what I like most about Wilson speakers.
Price wise, the 5s are the proverbial "bargain" in the Wilson line up. I would not trade out my 5s for 6s straight out (unless my plan was to sell the 6s for more $ and buy the 7s).
All this is said based on personal preferences and my preferences may (probably) not match others. I find that one must be willing to spend some time setting up the Wilson speakers to get the best sound, and to be honest, doing this with the Sophia's is easier (mostly because they are a single piece speaker and also IME a bit more forgiving).
I think the key is to listen to them, and in more than just one system. If you are listening at somebody's house, you need to determine what that persons goals are with the speakers - as they may not match yours and therefore set-up for different goals and objectives. It is also extremely important to note the amp and preamp used - the W/P are very responsive to changes in components, cables, etc. . . Again, recognizing the owners objectives or performance goals.
Finally, unless you like/want detailed sound I would not buy Wilson W/P speakers. To me, there is little point in buying them and then using all sorts of other components that are just going to soften them up/down. I like Wilson matched with neutral (not overly warm) amps. If you want rolled off highs, buy a different brand of speaker, IMO. Buying W/P and overly doing this with the other components is counter productive in my mind.