About not having potential on the sound in car, actually I sort of disagree. You don't need earplugs in order to fully enjoy a song and sometimes I feel like some songs are more enjoyable if you let the ripples propragate through the air around you. I don't have a spectacular sound system in my car, but it's pretty good and I can enjoy listening to music a lot in it. The outside noise usually doesn't bother, because the speakers create a surround unit that actually cancels the most annoying traffic noises.
Of course if you make a recording from inside the car you won't really get a good idea of the qaulity the person was listening when they were inside it though.
About the lyrics, the huge majority of non-japanese ayu fans became fans of her music because of vovals, compositions and arragements, not lyrics. The good lyrics indeed came as a bonus. If ayu had ****** lyrics I'm sure I'd still be part of this forum unitl today, while if she had bad compositions and arrangements but amazing lyrics, I'm sure I'd never have even joined this forum lol.
And while A Song for XX is about sadness and insecurity, the arrangements and compositions tell otherwise. I think YOU is a very beautiful song, so I don't feel like it's bad that someone will tell them the whole album feel is actually lovely, regardless of the lyrics.