I am very new to car audio and most of what is discussed here is a bit
over my head.

I have a Toyota Tacoma truck with a Clarion DXZ535CD Head unit and
Clarion 5 1/4" component speakers up front.  

These speakers are not amplified.

My main question is:

To be honest, I am quite disappointed in the sound having I switched out
the 5x7 OEM speakers and put in the Clarions.  The midbase volume was
poor.  The clarity of the treble is noticably better - as long as I
don't crank the volume.

When I do turn up the volume to get some decent midbase, I get a lot of
?distortion? from the tweeters.  They start crackling a bit with loud or
high frequency sounds.  I hope I have not blown them?

I am thinking about buying a 2 channel amp to supply the speakers.  I
think it will improve midbase to some degree but I am worried that I
will still have crappy sounding tweeters.  How much would an amp improve
the midbase in speakers of that small size and would amplifying the
speakers decrease distortion enough to stop the tweeters crackling?  Or
is it simply a problem of crappy speakers that amplifying will not help?  
Will I need to buy better speakers as well as an amp?

Also...

I have an MTX amp and JL 10W6 sub.  When I answer my cell phone I get a
lot of feedback through the sub when the system is powered on.  Any
ideas about a cause and / or fix for this problem?

And...

I was in SF last week and noticed that my rental car radio displayed the
song titles / artists that were playing on the radio.  I think my HU has
that capacity, does it?  Regardless, I cannot figure out how to display
that info, even CD info is not displayed.  Is it because I live in the
Great White North or am I missing something?

Thanks in advance for the help.

Neil