going from shop to shop listening to 5.25"s myself

That is place to start, but be aware that the sound you hear from a speaker set in the demo room of a stereo shop may or may not sound like those same speakers installed in your car. The acoustics (room size, wall shape, reflectivity, etc.), the sound source (head unit), and sound processing (amplifier) will be completely different between that room and your car, and all those things will color the sound considerably.

A speaker that sounds clean, accurate, and undistorted in the store will still be that way in your car -- but the... ummm... ambience of the sound may will be different.

You can get an idea of speaker quality, but don't expect that idea to translate literally into the environment of your car.

tanstaafl.