I think you should get:
"St. Louis Woman" Encores! cast to get a flavor for Harold Arlen.
If you want to be overwhelmed with beauty and good feelings get the OBC recording of "The Most Happy Fella"
"Company" is a good entry into Stephen Sondheim, get the OBC recording.
"The Rink" is a good Kander and Ebb score that I think would be suited to your tastes.
"The Human Comedy" is a lovely score by Galt Macdermot (Hair) and I think fits with your tastes. Like "The Rink" we are lucky to have cast recordings as both musicals were 80's Broadway flops. For that matter, you would probably like the OBC of "Baby."
If you can still get your hands on the remastered Kritzerland reissue of "Promises, Promises" OBC recording it is a must and a great example of contemporary pop sounds mingling with theater sounds.
"In Trousers," "March of the Falsettos," and "Falsettoland" comprise the Marvin Trilogy and all are very good if a bit esoteric at times. I think you will be take aback by these scores. If anything you must get the latter two which comprise the Tony winning Broadway musical "Falsettos."
"Happy Hunting," sure, but get "Gypsy" OBC first. =)
With Irma you gotta do something!