Moog synthesizers

[AstroSpec at aol.com]

I was wondering if anyone could give me an idea of moog synths that  seem to 
offer something original or worth having around in terms of sound. My friend 
currently has an opus 3 and a rogue, and he was told that they were both 
lower-class moogs. Is it possible for someone to give me a rating scale of 
the whole  moog synth line or separate the good ones from the bad?..thanks

matt