If you're looking at the Peavey Rockmaster for a child, learner, or hobbyist, I would look for similar features within the amp: affordable, portable, basic. For this reason, I would choose to purchase a mini amplifier for the Rockmaster. Battery-powered amps could also be worth looking at to tick the same boxes. Really, any amp would be compatible with the Peavey Rockmaster, but it depends on the sound quality you want and the budget you have for what would be the most suitable.