Michael: I too was in that position with a perfect pair of 1970's JBL Studio Monitors.
If there was one Gauge that rate a speakers
ability to Re-produce the Instruments just as they were Miked you could put in front an any set & make your choice.The reality is that The Recording Mixer,the Studio Acoustics,the Equipment & Equalizers,the re-mastering & the quality of the Formating all come into play. Now your Own electronics,Cables,Acoustics will also alter your sound- The new Manufacturing
techniques & Materials are vastly superior to 70,s 80, or even 90' products. When I
hooked up a Pair of High end Wharfedales to my $8,000 worth of gear I was blown away at the Music I never heard or heard with too much Noiseness..The soundstage opens up,The
bass cracks like a snare Drum with no Mush.
The mids & Highs trail off in a Orchestral fashion. For precise Re creation of Musical
instruments- Get a new pair of Towers and Wharfedale,Quad,Spendor,Naim would be a great place to start your journey.