Based on my listening in my dealer's place, both speakers well set up, the general feeling I had was that there is a noticeable difference, the Watt/Puppies are more revealing and go deeper in the bass, the Sophias are decidedly more forgiving of electronics upstream, perhaps a little bit warmer in the upper bass. Both are fine speakers, and the better the sources you have, the better both will sound--Goatwuss is right that neither speaker will be a bottleneck, and I like his advice that you should hear the Watt Puppies rather than buy them without listening to them. Both perform equally well in a room your size, they do not have a significant difference in the ability to fill up that size room. Can't comment on the JC-1s, never heard them.
On your point about the Sophia being a newer design, that's not really true--as I recall, the WP6 was revised to the 7 because the Sophia was so close to the WP6 in performance.
On your point about the Sophia being a newer design, that's not really true--as I recall, the WP6 was revised to the 7 because the Sophia was so close to the WP6 in performance.