It's a great question. The parts book would really tell the tale. From what I understand the Pro lineup consists of their helm 2.0, ram 6345, and the hose which have Kevlar reinforcement. Yes the hose are rated to 1500 psi but I'm pretty sure it's because of the hydraulic expansion that occurs when doing extreme performance type applications. In our world it's not nessesary. By that I mean boats with quads or racing boats doing 80 mph plus. I think without looking at the part book you won't find the little difference in the ram itself. I know they made it stronger with stronger hardware.
You could for sure use a pro helm in place of a 1.7 if you wanted to use it as a normal steering system on a sport fishing boat. I would just assume it won't have the same feel but I could be wrong. They might have improved the 2.0 helm feel when they went to the Pro lineup. The more fluid you flow with each turn comes wheel resistance.
Basically think of it like this. For the hydraulic pressure to raise up past where the standard hoses are rated to, you would have to add that much more resistance to the system, and for that to occur you'll need to be stressing that system all the way past that standard rating. The ram and hardware will also have to be rated for that beating for Seastar to assume liability and provide warranty.