For serious listening I run a Line Magnetic 805ia with my O/96's with fantastic results...very emotionally engaging with a dynamic, massive, immersive soundstage full of air and detail while providing a rich textured sound and a bit of that SET magic. I also have a SugdenA21SE that I run mainly for casual/background streaming music while I'm working during long periods of the day. I'd say the Sugden gets me 75% of the sonics of the Line Magnetic. While the Sugden is great match with the DeVore, delivering a very rich and dynamic sound, it's presentation sounds almost 2D in comparison without the air and soundstage of the LM. The Sugden also sounds a tad rolled off in the bass comparatively and loses in details.
I strongly recommend going the SET tubed route with the O/96's. Having some extra power (like the 48W of the LM805) really helps control the O/96 woofers. A 20W-40W push-pull amp using EL34/6L6GC (like the Leben) would sound very good as well. The Leben CS600x will give you a ton of flexibility to tube roll. Head to head I think the LM805 sounds more dynamic and brings that SET magic to the table that the Leben doesn't but it's a matter of preference.
I think 300b could be a magical combo for certain music but the more I talk to other O/96 owners the more I realize that a 300b probably shouldn't be a primary amp for the DeVore's as you may feel that the combo doesn't shine across a full range of musical tastes - focusing mainly on its brilliance with vocals and simple instruments.