Is the upgrade from Scout 1.1 to the Prime worth it?

The OP listed a MM only phono stage.  Kinda hard to drive a low output MC.  I agree that the Prime could use a better cart, but an Ortofon Black might be a better option.

I just setup one of the new MOFI UltraTrackers ($499) and am pretty impressed with it so far.  The MasterTracker is even better.

The Prime is a much better turntable but actually to improve
the sound resolution much more would require a MC cartridge.
I think that you would find that even on your Scout changing to
a MC pre amp or using a step up transformer such as one
from Bob's devices paired with a good MC cartridge would make a huge difference. 

I also went from a Scout 1.1 to a Prime. As good as the Scout is, there's no comparison. Agree with the posters recommending a cartridge upgrade. I went from a Ortofon 2M Black to an Ortofon Cadenza Bronze plus Bob's VPI SUT. The sonics are outstanding.

Thank you I really appreciate all of your opinions. I think I will make the leap to the Prime. I will also likely upgrade the Bronze to the Black until I can afford to do a nice MC and step up at the same time.  I will be back for recommendations.

I have a Scout 1.1 and had the original Soundsmith Zephyr on it for about 3 years. Sounded great and tracked well. Then I upgraded my phono pre to a Chinook with NOS tubes, and got the Soundsmith MIMC Star cart and it was a big improvement. Rest of system similar to yours

Primaluna Dialogue Premium amp
PL Prologue Premium pre amp 
Martin Logan ESL speaks
Running Springs Haley power conditioner

I am quite happy now, but one day may move to the Prime and am sure it will be the right move. Check out Soundsmith, lately excellent deals on them. Will get my original Zephyr retipped soon as a backup cart.