What, you don't have WHOOP UP? or KWAMINA? or FLAHOOLEY? You can't call yourself a true Broadway collector unless you have at least one of these "fabulous flops." LOL
Actually this could be the start of a new thread...what FLOPS do you absolutely adore?
Ok back to seriously....
CABARET wpuld seem a must, both the 1998 Revival and 1966 original casts are worthwhile.
I just saw the Toronto production of TICK TICK BOOM and if you like RENT you will probably like this one.
THE LAST 5 YEARS is well worth having as well.
But your list is missing some of the all-time great OCRS : OKLAHOMA!, CAROUSEL, MY FAIR LADY, GUYS AND DOLLS, GYPSY, FIDDLER ON THE ROOF, ANNIE GET YOUR GUN, COMPANY, A CHORUS LINE....
Don't neglect the older shows! There is much to learn about how we got here from there.
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