What's with the PJ amps and their like.... 5000000 5" speakers?

How good is a 5" speaker for tone anyway? I can imagine it having a lot of clarity, but how about low end?

I'm not considering getting one at all, but I just found out about them and I think they look ridiculous.

They're meant to be very very clear and responsive. They won't colour your tone in the way that an Ampeg would. The design of the cabinet is responsible for the amount of bass you can get from small speakers.