I would also take a look at the source(s) that you will use - see how many volts they output and take a look as well at the required voltage input for maximum output of your amp.
Most sources output around 2 to 2,5 volts but not all.
My vintage Sansui tuner (TU-717) only output 1 Volt. For example, Decware Zen amps need close to two volts for max output. This means that I would never reach the max output with that amp with that tuner (at 1 V) without a buffer (like my Burson audio Buffer AB-160 - which adds 6 dB). This is not a problem with Yamamoto DAC (YDA-01) with 3,1 Volts output. On my other DAC (Wyred4sound), I can play with the settings (between 1 and 2,6 Volts)
Just to say that if your source does not output enough voltage for your specific amp. - you will not get the max watts from it and if you are already at the lower limit … it may screw up all other calculations about speaker's sensitivity and all. But maybe you already looked at that.