Moving away from inefficient/low impedance speaker in order to move to a Tube Amp

why not try one of the better reviewed Chinese tube amps some of them are quite good and you can get 50-100wpc easily. Willsenton R8 for example is quite good for the money and very well built. made in the same factory as primaluna etc. 

another option is vintage or older tube amps as the tech has not really change much in the last few decades other than refinements. There's a ton of quality use tube amps that will give you more power to drive your speakers and give you more head room. 

some examples: current adds here. 

Line Magnetic 211IA | Tube | Detroit, Michigan 48214 | Audiogon 35wpc

Black Ice Audio F22 50wpc balanced integrated tube amp | Tube | Bluff City, Tennessee 37618 | Audiogon 60wpc

VAC Avatar Super Stereo Integrated Tube Amplifier; MM Phono; Remote (35148) | Tube | Erie, Colorado 80516 | Audiogon

VTL IT-85 | Tube | Houston, Texas 77069 | Audiogon

I have an Audio Hungary Qualiton X200 matched with QLN Prestige 5 and it is audio heaven. I have owned several Ravens and would not recommend for a speaker below 92 db. As a matter of fact the best match for the Raven Blackhawk is their CeLest speakers they are great speakers, James is a excellent speaker designer and they have a gem.

Focal speakers have above 92db models. And they are pretty decent speakers. 

Right now I drive 948s with Single Ended amplifier

Although a speaker's sensitivity should be considered when matching them to an amplifier, it is wrong to use a speaker's sensitivity rating as an indication of quality. Many speaker designers opt to trade high sensitivity for deeper bass reproduction, especially in a smaller enclosure. Remember also that a tube powered amplifier will seem more powerful and play louder than a solid state amp of the same or similar power rating. 

Another way of calling loudspeaker efficiency/ sensitivity is: dynamic compression.

When the loudspeaker has no dynamic compression, it is capable of giving all the amplifier put out, then it translates to 100% efficiency which is 112dB/Wm.

An ultra-efficient 102dB/Wm is 10dB down from that, that is: it has a 10dB compression already. It's not just peak SPL drop! It's the dynamic range being compressed.

Thus, using 102dB/Wm loudspeaker is like adding a 10dB dynamic compressor to the music. The 92dB/Wm speaker adds a 20dB compression, and a 82dB/Wm speaker adds a whopping 30dB dynamic compression! Now, combine that with the compression that is applied to the recordings, and no wonder the playback sounds so lifeless!

The dynamic compression of the loudspeaker is the primary reason we can tell it's recorded music, not live.

Going for higher power does not restore compression, so a 82dB/Wm at 100W is not equal to 102dB/Wm at 1W, although both produce 102dB/m peak volume: yet the range is 20dB diminished for the 82dB loudspeaker vs the 102dB one.

If you feel that you are hitting a brick wall with your system development, then you can try going for more efficient speakers. Be warned - the higher the sensitivity, the more the system weak links are exposed. Go above 100dB/Wm, and the exposure of weak links is absolutely ruthless. The clothes of the emperor are revealed....