Which amp matches best my JM Lab Mezzo Utopia ?

A friend of mine uses a LA audio 300B amp (mono amps 8 watt), it's a very fine combination. 3.8 Ohm isn't that low, if i remeber right they have a efficiency of 92 db, i think this is more important.

I read somewhere that it's not recommended to use SET amps with speakers that have impedance below 8 ohms.

If using a balanced amp on the unbalanced input : do both halves of the amp operate or not? If only one half of the balanced circuit and no intention to use a balanced source then buying a balanced amp is a loss of money. Anybody?

Sensitivity of the Mezzo is stated to be 92.5 dB. It is measured up to 2.8v. In 4 ohms this is not watt/meter. 2.8 v makes it watt/meter in 8 ohms. The sensitivity of the Mezzo up to watt/meter is somewhere 3dB less - 89.5 dB as the reviewers have measured it and stated it does not correspond to specs but without explaining the reason.

thats not vey demanding load i would get something soft in the top end for the jm labs