Its really not something that makes a lot of sense these days with multi-miked recordings because any one signal chain could be in or out of absolute phase.
So you get the horns in absolute phase but the drums are out. Its a 50/50.
The beauty of recorded music is that, unlike with food, you're not limited to fare just made "these days"
(Just some friendly ribbing, James)
Even if you believe that current multi-mike recordings don't reveal the benefits of correct polarity (and I don't), 95% of my music collection is stuff either recorded a rather long time ago, or if produced recently, recorded with attention to phase coherency. Absolute polarity switching for me is a crucial feature to have, somewhere in the equipment chain. The preamp makes the most sense from a practical standpoint, especially if you have analog sources. In a purely digital system, I think it's best accomplished in the DAC. Like Elizabeth, I listen to Maggie's, where the effects are likely more noticeable. But many "box" speakers, including Bryston's offerings, are touted to be phase coherent, and should easily show the salutary effects of correct absolute polarity.
REDBOOK, trust your ears!