I drive the NX Studio Monitors with a Line Magnetic 218ia. This is a decade old 845 based SET. Rated at 22 watts per channel it has no trouble playing at volume levels that occasionally peak at 90 db. Average levels probably ranging from high 70's thru the mid 80's. This is a small room as well with a volume of less than 1000 cu. ft. Being that I've always found SET's to sound far stronger than their rated power, I wouldn't be opposed to trying a 300B amp in this room. That said, the 845 has been a very satisfying tube over the years to my ear. Sorry, no experience with the 805.