The Clash, for the love of god, listen to The Clash. Other than that, it's tough to say what punk was, and who knows what the hell it is now. Some say the Talking Heads were punk, others say new-wave (listen to them anyway). I'd recommend DK, Misfits, Iggy and the Stooges, the MC5, Gorilla Biscuits, Op Ivy, The Circle Jerks, The Queers, X, Social D, Black Flag, The Ramones, The Descendents, The Buzzcocks, Stiff Little Fingers, Propaghandhi, Pennywise, The Damned, the Exploited, Crass, The Germs, and The Pixies all ought to give you a decent primer in early punk, hardcore, and the later pop and ska influenced punk.
As far as Op Ivy's stuff sounding poor, it's because it was recorded cheaply by some rather poor musicians (outside of the bass player). I'm not saying that they're a bad band, because the importance of Op Ivy is more because of the influences they brought and the sheer energy they played with. I bought their tape when it first came out and wore it out. In addition, 2 of the members went on to form Rancid.
