Hi...
this is a very nice system, I saw this before wthin the Audiogon user systems...the Lafon's in that specific version are very rare and are just gorgeous. A friend of mine has the same (with WE 300B) and they sound magical.
I have org. Altec Valencias with the same drivers and they will need only 5w to be on the safe side. I listened with Shindo Palmer 300B - 5-6W and they fully satisfied even with harder music (e.g. Einstürzende Neubauten, Joy Division...)
I listen actually with a 12-14 W Shindo PP amp, Pavillon Rouge, which sound somewhat more authoritative but I would think that this is rather something in regard of chararcter of the different amps than a matter of power alone. A good 300B like the Lafon will be more than sufficient in terms of power and control with any kind of music on these speakers, even with electronic music.
Best regards and much fun with that system.
Ron