SET v. Pushpull

At 85 dB sensitivity I wouldn't even go with any tube amp, at-least in my case. 

Not sure when people say SET watts are more than SS watts, but watts are watts. It is just that when driving to spec SET distortion is more pleasant then SS. But why listen to distortion (I prefer not to)?.

Pulsars are 83 dB efficient?. Not sure why specs on website does not talk about Pulsars sensitivity?. At least it says impedance does not get lower than 6 ohm that is good.

50 Watts will get you to 95 dB at 8 feet for 83 dB speakers.

If you get a good amp that puts out the watts your speaker needs for your listening needs without breaking a sweat you should not hear a difference. Basically non-existent distortion for all the watts your music needs. This is difficult at loud levels for fair moderately efficient speakers. What I have learned is to not to drive an amp to its spec.

If you want to go in the SET direction then may be pick a speaker that is close to 98 dB or even 100 dB sensitivity?. Then 10 to 20 watts SET will get you there given impedance does not swing. It is a bad idea to pick speaker after choosing an amp, in my limited opinion.

I do own Line Magnetic 508ia and it puts out 48 Watts for a price that is hard to imagine!. It sounds great at moderate levels on 92 dB paradigm studio 40v3 (when compared to Marantz SR7005). It seems it may not be good enough for new set of speakers I got myself, so I am on the fence with this class A tube thing.

If you can do true A/B test of AMPs, after level matching the SPL level,  you should not hear any difference at normal listening levels for good amps SET/Push-pull/Class A/ClassAB or Class D etc.

To claim all types of "good" amps adjusted for level sound the same is ridiculous. A 5 point penalty is charged.

@wolf_garcia guilty!.

No, push-pull doesn't entail more distortion. The exact opposite is true. SET amps always produce vastly more distortion at the limits of their class A envelope. Several whole percent numbers isn't uncommon. A similarly rated push-pull amp will easily achieve less than half the distortion with no feedback. A SET should really only be used with very efficient speakers because the distortion gets real ridiculous if pushed hard at all. And they have NO headroom above their rated power. Push-pull class A amps just transition to class AB with a small distortion penalty and keep pushing power. 
There are single ended/push-pull hybrid amps out there that are single ended up to 10 or 15 watts, than transition to push-pull at higher power. 
People typically like SETs for their distortion; robust amounts of second and even order distortion. You can get similar distortion characters from push-pull amps too, without the severely truncated power limits. An amp with a single ended input stage and a push-pull output stage is a good compromise. 

A nicely restored pair of Dynaco Mk III's will work well with your LS50's. PP 6550's and excellent transformers - 60 + watts from a proven classic design! Competitive in SQ with today's much more expensive tube amps!