I'd recommend this CD, "Epic In Minutes" over anything else. It collects all their 7"s and demos up until they started doing limited edition 12" in differenct languages n shit. "Police", "Litany", "Baiting The Public", all great Poison Idea-esque hardcore tunes with some killer almost-glam, hard rockin' guitar bits. From there they get a bit silly, I mean I love the idea of bands pushing the boundaries of hardcore but there's a reason why noones put a whistling solo in a punk song before.
Re: "what's the point of writing really great lyrics if they are not decipherable". Darby Crash wrote amazing lyrics but man, image him singing in a decipherable way. That'd be balls. I see what you mean but sometimes it can add mystery I guess...