I did the eyes close/open comparison and the difference was not huge because I had their location in my minds eye. Maybe they spread a bit more with closed eyes but I could still localize.
I read that the reduction or loss of one sense can lead to enhancement of other senses. For example, if you go blind your hearing can become more acute. It would be an interesting experiment to be led into a concert hall with blinders on. Of course part of the fun of the live event can be the visuals - watching the conductor and musicians, and generally the event as it unfolds.
I wonder if we were not predominantly sighted creatures if we'd use a similar vocabulary as we do now to talk about this stuff - which is largely a visual vocabularly. Then again, ostensive localization - there, over there, pointing - doesn't seem dependent on sight. Localization seems such an 'ancient skill', a survival skill born across centuries. When, in the dead of night, the twig snaps behind you...
I cannot imagine not being able to localize based on the pitch and timbre of orchestral instruments alone.
Before going to a performance it's fun to check the composer's orchestration even if you can't read a score. That'll tell you how many of each instrument the composer intended. (Though the local may not always follow that.)