Those are keepers, I would not sell my 20i set for that price, but keep looking and jump when 350-400 presents itself. It will.
You need the correct surrounds--thin, very flexible, and 17mm radius, or you lose the bottom octave. Thanks GordonW!
On some music/rooms/amps the 10's sound better. Apples/oranges. You can probably get away with not recapping 20's right away...but listen very closely to make sure the tweeters are working.
50 wpc? Uh, not unless it's a Pure Class A Pass Labs or tube amp. For SS try 160-200 at least (unless you have a nice sub). Unless you like clipping and replacing tweeters.