With speakers at efficiency at 98dB I would go low watt.
I run a 4 watt Decware with a 92db Ref 3A de Capos and the sound is amazing
my second system has a 2/6 watt Grommes PHI-26 with 97db Klipsch Quartets and damn does that sing.
With your speakers you have lots of options for low watt tubes