Spirit was a cool mix (ok so I'm only 26 but consider myself knowledgeable on the 60's/70's rock) If I'm not mistaken the way Spirit was started was 3 kids got together to play but they had no drummer, so the lead singer/guitarist had a Dad/Step dad that was already a famous Jazz drummer and it really made for a good sound. The drums on Spirit rock!!
If your digging on Crimson (Court of the Crimson King especially) you owe it to yourself to check out Emerson Lake and Palmer I suggest the self titled and Tarkus (those 2 are probably most like the old Crimson). Greg Lake is the Bass player on Court of the Crimson King and I do believe ALL the vocals on that album is him aswell. On King Crimson 'Wake of the Posidon' Greg Lake does vocals only.
Anyother 2 bands I would suggest along the same lines is Genesis (Foxtrot, Selling England By the Pound, Nusrery Crimes and Lamb Lays Down) these feature Peter Gabriel and all but the last i mentioned is Phil Collin as well.
Strwabbs is another to check out!!
See that girl, barefootin' along,
There's laughing in her eyes, dancing in her feet,
She's a neon-light diamond and she can live on the street