I migrated to 50 amp but had all of the electrical pulled so locating the new load center wasn't an issue. I also have a deck mount converter so no "shoe-in" required. The largest expense, by far, is the shore cord. If I had paid full retail for the Marinco cord, it would have been more than the load center, the breakers, and the power inlet, combined
A cheaper alternative is to install a separate 20 amp service and terminate one of your highest draw devices to that new subpanel. Or, you could probably use the same load center if you have an empty breaker slot.