Tommy, you're right. I feel worse because I don't know. Not that I'm ignorant, but I'm trying to do a quick'n'dirty swap.
Down the road, I plan on adding speakers, and evaluating the power of the unit based on what kind of speakers I want to drive.
For now, I bought the CD head unit from someone on this board, and just assumed it would swap right in. I assumed that it would use or have whatever low-power amp already was onboard (used by the cassette head unit). Could have been a bad assumption. I wonder if the behind-the-glovebox amp is standard (i.e. used for either cassette or CD units). I sure hope so.
The manual says there is a "key code" and I'm trying to see if anyone has any clue about that issue. The power issue, I haven't thought about. Maybe I'd better take the thing down to Radioman (local car stereo guy who certainly knows). Radioman, great name, what?
If you know anything about the standard power of these factory units (probably all lo-power units) OR about the keycode, please let me know.