PSVita is great for PS1 games and yes you can mod your 3.73.
Use "Final H-Encore 1.92"
Then use Modoru downgrader 2.1 that was released for 3.73 firmware and downgrade to 3.60
Thereafter start the web browser and go to the henkaku site to apply henkaku
Now Install enso (not enso ex)
Thereafter...