I have a Casio Privia PX730. It's a good unit, and I like it a lot. Today I felt like opening part of it up and have a look at the insides. I saw these speakers: They look like they're 4" - 4.5" in diameter. They're the crappy speakers with the paper cones. According to the manual, they're 7-8W rated speakers. I'm thinking - will it make any difference if I use a set of car speakers with a heavier magnet and better material like kevlar? I'm not too sure about the amplifier that drives the speakers. How would I go about changing that? Will leaving it as is, and underpowering a spare set of 'good' speakers do anything?