LP or CD?
That would make a huge difference to me. I don't feel my copies of Loveless and DN are that replaceable on vinyl.
That said, my LP copies of
The Beatles (my best condition numbered Apple/or my DMM German pressing--this would be a hard choice!)
Exile on Main St
Nasty Music (2 lp Stones bootleg, live 72 & 73)
Highway 61 Revisited (mono)
Blonde on Blonde (mono)
Ever notice how this place just basically, well, sucks.