Are coaxial speakers and midrange speakers the same? Nope, not at all.
Coaxial speakers are basically what comes stock standard in a car off the manufacturing belt – which means that they can produce a full range of sound. Basically, they are two speakers that share the same central axis and contain more than one driver, which allows them to produce a variety of sounds and frequencies.
Mid-range speakers are usually cone shaped and are part of what is known as component speakers. Usually installed in conjunction with woofers, tweeters and other speakers, they’re designed to produce a superior sound quality and are more customizable than coaxial speakers.
SqueakCoaxial speakers are two speakers that share the same central axis, hence the name. What bad venge said is pretty much correct with the exception of 6×9 coax (because 6×9’s aren’t really midrange drivers). From what you’re said, I would buy some 4″ or 5.25″ component speakers. Then install those and replace your current tweaters w/ the ones from the components. That should give you more mids, but you’re still going to have overpowering bass w/ two 10s and 6x9s (both are bass drivers).