Well, perhaps those low efficiency speakers will help you preserve your hearing longer in your life, avoid tinnitus, ... I never thought of it this way.
you can find much on the net, i.e. This site, scroll down some, says average Classical Concert is 90db, with momentary peaks of 120db.
http://www.audiodrom.net/en/as-we-see-it-tips-thoughts/74-realistic-volume-levelsthis one, posted above, scroll down, shows sound level lessening by distance, IN OPEN SPACE
https://www.puiaudio.com/pages/speaker-power-and-distancei.e. if you are 4 meters/13lf away, it is -12db. That is 4 meters FURTHER than 1 meter, so that is 5 meters/16lf away from face of speakers.
ignoring that the room’s surfaces will retain sound levels, or that there are two speakers: let’s do
some OPEN SPACE SINGLE SPEAKER math.
your speakers, 1 watt, 1 meter = 88db
sit 5m/16lf away -12db = 1w/5m/76db.
double the power in watts for each +3db sound level
to get to concert hall avg 91db, (5 doublings) math says you need 32wpc.
a 94db momentary peak will need 64wpc. (you mentioned 60wpc)
128wpc for 97db, keep doubling for each +3db peak
.........................................
Practically, the answers from people who have used low efficiency speakers with ____? wpc tube amps will give you the best indication, so tell us, or ask them:
room description
desired volume?
type of music, i.e. just loud peaks, or loud average?
length of listening sessions in time is also a big factor regarding hearing loss.