I was thinking about putting a head unit in the glove box, and then a CD-changer in the rear trunk, with a RF (not IR) remote control. Try to keep the dash as original as possible.
It turns out my GTV has a pioneer cassette player and a big hole in the dash already.
My choice is now a Blaupunkt Santa Fe.
Not too expensive, not too fancy, sounds pretty good.
I would like the interior to look close to original, or at least period correct. Now that I said that, I should probably just hack some big holes in the door panels and some Pioneer 6x9's in the rear parcel shelf, put an 8 track player in the dash! Not!