Here are some orchestral recordings on LP that will let you hear how well a system is performing. I've tried to keep mostly to some reissues that should still be available through the usual mail order sources (marked with *).
Stravinsky, Firebird, Dorati/LSO, Mercury SR90226 (Classic Records reissue)
Stravinsky, Le Sacre du Printemps, Solti/CSO, Decca SXL 6691 (Mine is the original and I haven't heard the recent reissued by Speakers Corner, but given their track record it should be good)*
Larsson, Concertino for Double Bass & Str Orch, Wedin/OskarshamnEns, Fredin -db, Opus 3 8502
Chabrier, Espana, Argenta/LSO, Decca SXL 2020 (Speakers Corner reissue)*
Kodaly, Galanta Dances, Kertesz/LSO, Decca SXL 6136 (Speakers Corner reissue)*
Varese, Ionisation, Mehta/LAPO and LA Percussion Ensemble, Decca SXL 6550 (Speakers Corner reissue)*
Ravel, Works for Orchestra, Skrowaczewski/MinnO, Analogue Productions APC 007 (Vanguard recording)*
Bartok, Music for Strings, Percussion and Celeste, Decca 6111 (Speakers Corner reissue)*