I have metas but no, not used a tube amp with those or prior ls50s.
I did use a highly regarded 180w/ch zero feedback SS amp (higher output impedance like a tube amp) with ls 50s the first time I ever heard them when another Agoner brought a pair over to listen and we were both quite unimpressed. THen hooked up to my current Class D SS amps and it was night and day.....very good. So I can vouch they can be very sensitive to amp used and are NOT designed to be used with tube amps so I would personally not go there with any ls50 for best results.
I did use a highly regarded 180w/ch zero feedback SS amp (higher output impedance like a tube amp) with ls 50s the first time I ever heard them when another Agoner brought a pair over to listen and we were both quite unimpressed. THen hooked up to my current Class D SS amps and it was night and day.....very good. So I can vouch they can be very sensitive to amp used and are NOT designed to be used with tube amps so I would personally not go there with any ls50 for best results.