OK, life is not always fair. When I was young, I had good ears and loved the stage and some harmonics pitchig of many high-end sound systems I had a chance to hear. Today I can afford installing a good system to my boat (I have Bose and B&W mix), but my ears can't tell me that difference anymore
Anyway, here Boss brand is very popular, and considered "D" class audio, but very cheap. Not sure about their marine line, but you don't need "A" either, I'd go for something in between like Clarion.