What tracks offer the best left right separation?

The Ventures, serious seperation.

Electric ladyland
Jimi Hendrix, duh.

From the 1950's: any Phase 4. Total left, right back and forth. Music snobs almost universally hated the effects. A new medium, stereophonic sound, was being experimented with, for good and bad. Ever since Phase 4, the industry has steered away from such "gimmicks." Soundstage almost becomes defined as a requiring a center performer, but not with Phase 4. It will challenge systems because performers are often 100% left or right. 

a good album, lots of stereo fun:
Los Machucanbos

The best separation is in heavy metal or alternative music from 1988 to 2000 by the major bands also on vinyl it is the old command records or anything from fine recording studios in new york city.

ET phone home.  

Was talking with Rick about this just the other day, coincidentally enough. Low bass (below 80) is all mono. There is no such thing as stereo bass. This is easily proven, which is how I know, I tend not to take anyone's word for anything. Ran the subs stereo, ran them mono. No difference. It is all mono.  

However while the bass signal itself is most assuredly all mono the way we hear it most definitely is not. Everyone who has heard my system notices the superbly seamless bass imaging. It sure seems to be stereo! But again, for sure it is not. Sounds exactly the same when run mono.  

So what is going on here then? Well for one thing every note regardless of frequency is chock full of harmonic overtones. One octave up from 80 is 160, and we for sure can localize that. So all that has to happen is our hearing centers use that to form a mental image and localize the lower frequency fundamentals.   

That's all it is. This also explains why more subs such as with a DBA produces even more articulate and dimensional bass than just one or two. No matter where you put the one - or two.  

Another one of those things people have a hard time understanding- but recognize immediately when they hear it. Which they definitely do when they hear a DBA.