[Major Tom]

I don't know how long the power cord is on that amp, but many amps including my Peavey Bravos come stock with annoyingly short power cords, maybe like 5 feet or so, that always seem to be just a foot short of reaching the outlet. I changed mine - just the extra couple feet of an 8 foot long cord seems to reach where you need it to go... Cheaper amps usually have the less expensive vinyl insulation power cords - works ok, but they tend not to lay flat, retaining the coiled up shape, tripping hazard....This would be a good excuse to put a proper 8 foot, rubber insulation power cord on there.

Yes, you want that third prong. Its not necessary in the perfect environment, but anytime there is a problem like an outlet that was replaced and wired backwards in combination with other chassis-grounded devices, or if an internal issue developed in the amp itself, or other problems, electrical shock could occur. That is a protective / safety thing, much like the seat belt in a car - you'll never know when you need it, and it might not be your fault, but when something goes wrong you want it on there. Remember, your guitar's bridge and strings are connected to the chassis ground of your amp.