Recommendations for a car stereo set-up?

Hey fellas, I am planning on installing a nice and loud car stereo in my '75 Scamp. I was looking at a Pioneer unit at Best Buy and a 45 watt amp.
For now I just want to run two 6x9's in the package tray.

Issue one: I don't like the space age look of the speaker covers on the speakers I saw. Have any of you mounted the speakers from underneath and just have the factory speaker cutouts in the package tray? WIth the 3 way and 4 way speakers I saw, I wonder whether there would be clearance issues with the package tray since the speakers are not flush on top. know what I mean?

Issue two: Where should I mount the radio? I don't want to cut the dash, so I would like to install under the dash. My car is an AC car (not working) so I have the three vent unit under the dash which I removed. There was a generic under dash mounting box at Best Buy I saw, but it looked HUGE.
ideas? thoughts?
Thanks!