300B for LS3/5A?

Their impedance should make the Rogers an easy load on the amp, but unless you are wearing your speakers as headphones I don't think your going to be very happy with the volume levels that you are going to achieve. Just my humble opinion.

Some die hards were claiming they are actually a good match! Are there owners out there?

I drive my LS3/5A's with 2A3 SET (3.5W) in a small room with very good results.
If you have a small to medium listening room,300B amp would have no problems.
Bass control and dynamics will not be comparable to a good SS amp,however you will have all the midrange magic of LS3/5A's.
As Mcfarland mentioned above,with 300B you won't be able to go very loud.
All this IMHO.

Will run them but best to match loudspeakers to amp at 11ohm great but 82db 1 watt. Your at the bottom end or far past of what a SET can drive. Might be great for nearfield but dynamic range will suffer. If your sold on the wee BBC monitors and SET look for a 845 or other higher power SET. I see many running loudspeakers that are at the xtreme of what a SET can drive most give up on SET after. Or on forum they go saying SETs distort, have no bass,can not produce much SPL etc etc. Best to SET ;0 up system right from the start. Make sure amp loudspeakers are a good match.

I have heard 300b driving the 15ohm version with very good results even in a living room! But not sure if 11 ohms would make a different?