I know the Viper 4+ setups are loved by everybody so I'll assume they are good.  My 4430 had a Viper Pro when I got it and after half a season I converted it to a Pro 700 system and used the display, NAV, and 372 I had on my combine.  I spent about $5,000 on the autosteer valve and harnessing and also had to replace the Boom Control Node.  For what I wanted to do it made my life a lot easier.  I'm able to use the same auto steer lines I have in my tractors.  I've since purchased a dedicated Pro 700, NAV and 372 for the sprayer so I don't have to swap back and forth.  All my fields are setup in the display.  All my lines are in the display, and the RTK works at 14 mph down 30" rows.