Here is Brett's first reply:

Here are the basics of my system:
Alpine head unit in the glove box
Kenwood 4 channel amp in the trunk on the rear seat brace
two 6x9 3 way speakers in custom enclosures to fire forward
towards the area where the top folds down (oly place sound
comes through relitively unobstructed)
One 8" Kicker Free Air subn mounted on the rear seat brace
two Aura Bass Shakers under the front Seats (25w each)
Two 4x6 plate speakers in the stock Kick Panel location with stock grills
one shallow 10" speaker to replace the stock front speaker.

I will be adding another amp to help out, but over all it sounds pretty good
for being in a convertible with nothing visible!

Tell you more soon! - Brett! - 67 Drop Top 455!