Hdip said..
For the river, I'm not sure you'll get the true benefit of the X series. The X series is all about hitting white water in waves. Controllable roll and reentry on airs.
Compared the the S you will lose glide. The S is the all around series from Code and hard to beat unless you're trying to specialize in one specific aspect.
Can only speak from my experience with the 810X at 87Kg. I've mainly PW downwinded the 980S in all the the usual Gorge wave spots, last and this season but wanted something smaller for the big days. Would have prefered an 850S but buying a new three season old foil seemed like financial suicide and this 810 came up used, so I jumped on it. It took three sessions or so to get used to it but now I'd never give it up. Anytime I can use a 3m or smaller doing Rufus runs or in the corridor I'll be on this, it's so forgiving and rolls so fast.
I would agree though there's still untapped potential there in breaking waves.