I'm a very satisfied owner of Dynaudio C4's. My room is similar in size as your room (21' x 16' x 7'). C4's in your room will greatly benefit from room treatments.... failure to treat a room your size will result in the C4's overpowering the room and you will be dissappointed. I recommend GIK Acoustics room treatments... $600 to $900 spent on room treatments is one of the best investments you can make in optimizing your speakers. I also recommend the Plinius SA-102 amp with an Aesthetix Calypos preamp with NOS tubes (Telefunken 12AX7 smoothplates or Mullard CV4004's)
The Wilson Sophia's powered with tube gear would also be a fine choice and may be better suited for a room of your size.
The Wilson Sophia's powered with tube gear would also be a fine choice and may be better suited for a room of your size.