Although specs obviously don't tell the whole story, and in particular don't say much about how the amplifier's sonic quality will hold up as its maximum power capability is approached, fwiw:
40 watts into each of two non-planar speakers that are 92 db/1W/1m will result in a sound pressure level at a distance of 10 feet of about 101 db, which seems pretty reasonable for most listeners for most music, especially given your preference for light jazz and vocals.
I have a lot of hi-res (24-96/192) so I think dynamic range is important.
There is a subtle but important distinction relating to the difference between the dynamic range of the music (that I was referring to) and the dynamic range of the medium.
The 24 bit dynamic range of the hi rez formats greatly increases the fine detail that can potentially be captured in the music, as well as lowering the noise floor, in comparison with 16 bits. However, as I was using the term the music itself will rarely have a dynamic range of more than around the 40 db number I referred to, and will (especially for rock music as it is commonly produced) often have a dynamic range of well under 10 db.
"Dynamic range" as I was using the term refers to the difference in volume between the softest and loudest notes of the music, where each of the two volumes represents the sum of all frequencies that may be simultaneously present. What the much larger dynamic range of the medium makes possible is accurate resolution of EACH of those frequency components.
An example illustrating that distinction would be higher order harmonics (overtones) of the fundamental frequency of a note, that are important contributors to tone and timbre. For accurate reproduction of those overtones a medium providing very wide dynamic range (ideally 24 bits or more) is necessary. However, those low level overtones don't contribute significantly to the dynamic range requirement I was referring to, that is an important determinant of the maximum power capability that is required, and which is based on the SUM of all fundamental frequencies, harmonics, and broadband spectral components that may be present at the times the music reaches its highest and its lowest volume levels.
Given your musical preferences, the 10 foot listening distance, and the 92 db/1W rating of the speakers, I would guess that you would be ok with 40 watts. This statement in the manual provides some added confidence in that conclusion, as well:
A great deal of attention during design of your new SLI 80 was concentrated on the "overload recovery" ability of the amplifier. The ability of an amplifier to instantly recover from clipping is much more important than is commonly believed. In the power war of amplifier manufactures the mentality is focused on high and then even higher power output to solve the clipping problem. When in reality the most critical aspect is how fast a recovery an amplifier can achieve after overload. Most of the music being listened to in an average listening room is only requiring about 3 watts of power. It is on the transients of loud low frequency program material that tremendous signal voltages will appear at the input of the amplifier. It is in this situation that the overload recovery ability of an amplifier is of critical concern. The SLI 80 will overload symmetrically at any frequency in the audio band-pass. The SLI 80 will also yield faithful reproduction of extremely low frequencies at full output levels. Power transformer, power supply regulation and output transformer design and careful shaping of the overall frequency response curve all play a very important part in the ability of the SLI 80 to recover quickly when overloaded. The high voltage rail will fluctuate no more than a volt between soft and loud passages.
Regards,
-- Al
