Ok, an update. Finally got the Nano, and after some issues with a couple of computers and iTunes, successfully managed to get my CDs imported.
Saw the Monster iPlay cassette adaptor at the store while getting the Nano - thought I'd try it out and get a cheap temporary solution until I decide on what I'm going to integrate into my car stereo. And to be honest, if the cassette adaptor worked well, I'd indefinitely put off spending a few hundred bucks to integrate my stereo.
Report on the Monster iPlay cassette adaptor - a piece of $%#@@*&!!!!@ crap. Doesn't even work at all. Goes in, I can hear a hissing, crackling noise, but nothing from the Nano itself. Tried popping in a regular cassette - that works fine. Tried it on another car - still nothing. Now I've got to go back to the store to return the piece of crap.
After spending a good amount of time importing all my CDs to the Nano this weekend, I'm a bit frustrated not to be able to play it in my car.