You were originally looking at the twin ram add-on which was $2459
Full system single ram $2399

The full system would eliminate any play in the steering and have much better response to input.

Well I was comparing dual ram to dual ram, but I guess that begs another question is the dual ram really needed?

I would think the helm would be the same

twin ram system would use more volume. Could work but instead of say 3 turns of the wheel you'd need 6.
A single ram helm may use 75cc per revolution were a twin ram would be 150cc per.

In your opinion is there much to be gained by having dual? Is one enough to take the play out and control the walk at 60 mph+?

Depends on boat size, weight , the sea's you run in and how hard you run.
And in my opinion, dual evens out the load.

I might be stating the obvious here, but before you sink your hard earned money into a worthy upgrade like hydraulic steering, you need to do something else first. That would be totally going through all of the steering pivot points in your drive to make sure you don't have any play / need to rebuild anything that's already worn out. Hydraulic steering - no matter which style or manufacturer you choose - will dramatically reduce wear and tear on your steering system and steering pivot points on your drive. It will not however magically rejuvenate worn out pivots. In other words, if you're going to do this upgrade, do it right to get the maximum benefits out of it.