There is such a thing as a good album/music/recording that doesnt sound very good by todays standards. Led Zeppelin for example. Genesis records. Early Motown, Elvis, etc. These older records suffer from low tech recording methods and often errors in the recording or mixing process than now cannot be removed. Remastering can sometimes help when its a decent record with certain kinds of mistakes, like a messed up EQ. With Genesis, your system will sound like it has absolutely no bass if you play back accurately.
Live albums almost all are compromised because you cannot separate the band from the room they are playing in. While Filmore East was a reportedly a good sounding room, "good sounding" in 90% of live venures rock bands would play in in the mid 60s sound horrible compared to a good venue today.
A second issue is The Allman Bros was recorded with far more basic gear and far less technology applied. Tom Dowd, one of the industry’s best early mixers, mixed some of those Allman Bros Fillmore East tracks. He was famous for recording a whole band with 4 or 5 mics- that was all he had. So the music is great, but the recording bandwidth is not as good as a modern recording no matter what playback system you use. And contrary to some thinking, ]the better the playback rig, the more accurate it is, the WORSE it sounds due to accuracy improvements that reveal more flaws.
The trick is to mentally separate the music from the recording. Don’t expect Allman Bros to sound good or use it to eval a sound system. "Its the music baby!" (said in an Austin Powers voice), Use something new like Lana Del Ray to eval a sound system.