You aren't going to get good sound with that head unit without an amp.
I would add a four channel amp to the system first, and see how the
speakers sound then.

If you're set on speakers first, I've had good results with Boston
Accoustics.  Pioneer and Sony are crap.  Alpines are somewhere in
between.  Phoenix Gold and Mission are the best I've used, but they're
out of your price range.

Mounting is a problem with the '69-'70 because the kick panels with the
speaker mounts molded in aren't available.   You could make some laying
fiberglass over your own mold, but that would do away with those nice
fresh air vents.  Realistically, you've gotta cutthe door panel.  In my
'70 Cougar I've got a 1" particle board build-out on top of the hole in
the door panel.  This allowed the use of a Mission mid with a really
big magnet, mounted in the lower front corner, and a tweeter up high. I
think that's the best way to go.

180 Out

Putting a system in a '69 is a huge PITA. Kick panels are out, cutting the
doors sucks. besides, the placement there makes the sound crappy no matter
how good your drivers are. If you have a rear deck, then you have a chance
for sound, but not quality. I have the worst of both worlds since I have
solid doors without factory speaker holes and a fold down rear seat. I've
been trying to figure something out for MONTHS. It's gonna come down to
lotsa fiberglass fabrication.

I still want to use the fold down capability but need to use the space for
the sub enclosure. I've already removed the passthrough door into the trunk
and made a mold of it. The mold will be used to build a plug to make a new
door which will be the face for the sub enclosure and a set of 6.5"
component drivers. Obviously the door would become non-functional since the
enclosure would intrude into the trunk.

I'm thinking of fabricating new kickpanels which include ducting for the
fresh air vents. Air would travel through the duct up towards the bottom of
the dash and would exit through a set of vents similar to the vents in the
center of an AC dash. It would look correct. Problem on the driver side is
the e-brake and release handle. FRACK!