Jadis JA30 Mk2, how great???

The JA30Mk2's with the Franco Serblin Accordo's would probably be a great match up. 
Agree 100% with the post above by charles1dad. 

So if wonder if the SE300B will sound as great if power/speaker sensitivity wasn't be a concern in this regard. Very interest to try the 300B as well for full range high sensitivity speaker. 

Samhvcc,
You express considerable interest in the Jadis SE 300b mono blocks. Although this is a PSET (Parallel single ended triode) topology it is rated at a relatively low 10 watts per channel. Typically a 300b PSET is rated at 16 to 20 watts per channel.

What this suggests to me is Jadis is more interested in achieving the best sound they can rather than extracting more power from the parallel 300b tubes. They chose to run the tubes at lower operating points (OP) to maximize sound quality. Higher OP parameters would easily provide more power.

Given Jadis’ established track record for excellent sound quality this decision is not surprising. To take maximum advantage of this amplifier’s potential I recommend the following.

Most important IMO is finding a speaker that’s easy to drive with low power. You want a relatively flat impedance curve that avoids wide fluctuations. You want a speaker with relatively high nominal impedance, say 6 ohm or higher.

Sensitivity of 94/95 db rated (measured) at 8 ohm impedance and even higher is desirable.
Both of these are important parameters but I believe that the speaker impedance and ease of driving are of higher priority for SET amplifiers.

For the SET amplifier itself output transformer quality and power supply quality are paramount but I feel that Jadis has this covered. Focus on speakers that were designed with the goal/intention of being used with low power amplifiers.

IMO the Jadis SE 300b will genuinely sing if paired with the right speakers. Best of luck to you.
Charles

Once again, some great advice from Charles1dad!
More than likely with the 300B Jadis amp, one is looking for a horn type of speaker. This aspect is another reason why i have never been that enamored of 300B type amps..and not because I don’t think they have the potential to sound good.