Thanks for the input. I've already tested out the cassette adapter and it's pretty (surprisingly) good.

The cost of a new head unit (which would require a new amp as well, plus installation) would be well over $1,000 and would still disable my steering wheel controls and computer integration. And, I'd have to pay all over again to return it to stock when the lease is up. It's just not worth it.

Besides, the sound quality you can obtain in any car is unacceptable to a 'serious music person.' In a car, you're competing with 80+ dB of background road noise, and that's with the windows up.