Great work Chris! Glad you used the criticism positively to improve your site. Those mp3s sound fine to my ears but I don't have super sound equipment in the first place, or any decent headphones.
Fact is mp3 is by nature a compressed “lossy” format so as you said you're never going to get 100% and it's all about a decent trade off. I think your site is a great convenient way for people to quickly catch up with some nostalgic tunes.