Just some info FYI. I got bored and wanted to calculate some things. Yes, I'm kind of an engineering nut.
This would be assuming the hydraulic pump works at 100% efficiency (It of course doesn't due to friction/heat) so the horsepower required by the pump would be slightly more than the horsepower output.
Anyway, at 2500psi and a 13.9GPM flow rate the 3320 is producing 20.27hp in hydraulic flow. This would be at the full rated speed, etc. Even the 3120 would have leftover HP at full hydraulic flow and pressure so any HP beyond that isn't going to help your hydraulics. (If you are moving or using PTO hp while doing that extra hp would come in handy. Also how often do we use full PSI. (Flow comes from engine RPM, pressure when loaded takes torque off the engine at that RPM).
My 2305 (A meager 5.2 GPM flow and a lower 2000PSI ceiling) only produces
6.07hp in hydraulic flow at full RPM and pressure.
For any closet engineering freaks out there here is how to convert:
HP = PSI * GPM * 231 / 12 / 33000
Notes:
231 cubic inches in a gallon
1 SAE horsepower is 33000 foot pounds of work per minute.