Perhaps I wasn't clear....

Rated power is what the manufacturer claims the amplifier will produce...

Measured power is well....measured...it's what the amp will actually do.

Cheap, flea market brands typically over rate their amplifiers (sometimes by a factor of 2 or more) to make them look better then they are. I've seen plenty of "2000W" Legacy amps that weigh 3 lbs and have a 40A fuse on the side of them.

Most of the good amplifier manufacturers under promise and over deliver - meaning a 50W amp really turns out to be a 75W amp. The old SoundStream and Rockford Fosgate amps were very well known for exhibiting this - that's why people call them under-rated.

As for it being good for one application or the other....it will work fine on any speaker, but it could be a nice addition to your particular setup to get a single 10" subwoofer perhaps to augment the current cabin speakers you have. It was just a suggestion. The amp is certainly capable to power those 6x9's or the front speakers!

Good luck!