Stereo in my 69 vert?

I don't know much about audi systems either but I have a 69 coupe with just a 4x50 watt Pioneer cd player, with 2 pioneer 4x6 or 6x9 in the rear and i beleive the kenwood dual dash speaker upgrade that you can get from just about any Mustang suppliers.

I don't remember for sure but I think my speakers in the back said 120w rating on them and they look to be like a woofer/tweeter combo speaker.

Loud enough to listen to music going 80 on the freeway with the windows down. The sound is good from lows to highs. A lot of people thought that I had some kind of complicated systems with amps and stuff but all it is is the head unit and speakers. Get a head unit that has a good amp in it and some speakers that are rated high enough to bump up the volume while still maintaining sound and you should be ok.

Audi system?

I'd get some 6.5" kickpanels/speakers, theres really no place on a vert to mount decent rear speakers, I have the 6.5,s in kick panels, 6x9's in angle shaped boxes on the floor that face up at a 45 deg angle behind the fron seats and 2 10" subs in the trunk with an amp. It sounds real good at normal speeds, when on the fwy you dont hear the sub woofs much at all.