challah,
check out this thread since you're music hunting;
pandora
i'm not really sure what musical styles you're chasing; in addition to the csn(&y?) stuff, a lot of the 60's/70's folk music might be up your alley..for instance peter, paul and mary do some really neat three part vocal harmonies.
roach will inevitably suggest you check out the eagles. if bluegrass / nickel creek hits you where you itch, you might try some Newgrass Revival (sam bush, bela fleck); they sound like a 70's hair band that picked up bluegrass instruments...so the vocals sort of sound like kansas or something. its a little fucking weird for me, being a moderate redneck and all. i think mudhoney has decent vocals (male), and perhaps something like teenage fan club. some people might say fleetwood mac. if you just want crazy vocal harmony, you might try some barbershop quartet junk. when i was 12, i somehow found myself listening to the nylons - did the cover of 'nah nah nah hey hey hey goodbye' that was so popular at highschool basketball games. some old school bob marley and the wailers with bob, bunny and tosh doing three part harmony are pretty tight. there was a guy in illinois named brandon washington who could belt out the sound, if you like the holyshit black male vocal sound. i ummm...can't find anything by him on the web, but fuck it why not?
good luck.