Here are some suggestions based on the titles you own....
1. Sondheim:
You have most of his scores but do get ANYONE CAN WHISTLE (OBC on Columbia/SONY)
2. Kander & Ebb:
You have their two biggst hits: CABARET and CHICAGO. Try THE RINK (on JAY), STEEL PIER (RCA Victor)and maybe ZORBA (EMI)
Don't waste time on THE ACT (unless you are a Liza fanatic) or THE HAPPY TIME.
3. Ahrens & Flaherty: ONCE ON THIS ISLAND (RCA Victor)
4. Jerry Herman:
MAME (Columbia/SONY)
MACK AND MABEL (MCA)
5. Cy Coleman:
SWEET CHARITY (original on Columbia/SONY)
BARNUM (Columbia/SONY)
THE LIFE (SONY)
LITTLE ME (1998 revival)
Don't waste time on SEESAW or WILDCAT
6. Bernstein:
You have all of his majr scores except ON THE TOWN (Columbia/SONY)
7. Lerner & Loewe:
CAMELOT (Columbia/SONY)
BRIGADOON (DRG)
PAINT YOUR WAGON (RCA Victor - good score but dated recording)
8. Richard Rodgers:
DO I HEAR A WALTZ
NO STRINGS
SOUND OF MUSIC
FLOWER DRUM SONG
OKLAHOMA!
PAL JOEY
ON YOUR TOES
BABES IN ARMS
THE BOYS FROM SYRACUSE
Cole Porter:
OUT OF THIS WORLD
CAN CAN
SILK STOCKINGS
ANYTHING GOES
Don't waste time on MEXICAN HAYRIDE or SOMETHING FOR THE BOYS
Irving Berlin:
ANNIE GET YOUR GUN (1966 Lincoln Centre cast on RCA Victor)
CALL ME MADAM (better to get the movie on DVD, no good OCR on CD)
Dont waste time on MISS LIBERTY or MR PRESIDENT
Jule Styne:
GENTLEMEN PREFER BLONDES
PETER PAN
BELLS ARE RINGING
FUNNY GIRL
Dont waste time on SUGAR, HALLELUJAH BABY or FADE OUT FADE IN but
SUBWAYS ARE FOR SLEEPING is fun as a "fabulous flop"
Jerome Kern:
SHOW BOAT (1993 revival on Livent is best highlights versin)
You also are missing major Tony winners: RENT, EVITA, HOW TO SUCCEEED..., FIDDLER ON THE ROOF, HELLO DOLLY, THE MUSIC MAN, DAMN YANKEES, PAJAMA GAME and KING AND I.
Best though to sample through local library first so you don't spend $ on Cd's you won't enjoy playing.
As for me...I collect them all!
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com