The MkV already puts out 200 W. Going to an 800 W is a 6 dB increase or one S unit at the other end. IMO it would be pretty rare condx when 1 S unit would even be noticeable, much less make a difference in bagging a QSO. You might get more bang for the buck by spending it on the XYL so she lets you operate more. Lou W7DZN