I have not heard the Croft so perhaps DQ has. Of course he has a vested interest. Nevertheless, the OTO SE is a lot better than the OTO PP. and in terms of power - it's not really a lot more.
It takes a doubling of power to get a 3dB gain in SPL. So an 18 watt amp that puts out 100dB from the speakers will need a 36 watt amp to get you to 103dB. The Cobra can't even give you that gain over the SORO. 3dB is not very noticable.
It takes 10dB to be perceives as "doubling" the volume level to your ear.
So if you have 90dB speakers with the SORO (P2SE)
90dB - 1watt
93dB - 2 watts
96dB - 4 watts
99dB - 8 watts (The OTO/P1SE)
102dB - 16 watts (This is the SORO/PS2SE)
105dB - 32 watts
108dB - 64 watts
111dB - 128watts (this amp will be "twice as loud to your ear over the SORO/P2SE)
114dB - 256watts
117dB - 512 watts
120dB - 1024 watts
Of course, many speakers have a maximum watt number so if the speaker can only handle 150 watts then it probably can't muster more than 112dB based on the chart above if the speaker is 90dB sensitive.
But most people listen in the 70-80dB range. If you download an SPL meter app to your phone - sit in your chair and measure how loud you play. People are often surprised that they are not listening anywhere near 95dB let alone 100+dB.
Further, add in the second harmonic distortion clipping (or soft clipping) of tube amplifiers and they are often perceived to be equal to SS amplifiers at 2-3 times the power - so a 20-watt tube amp seems like a 40-60 watt SS amp). All a lot to consider and if power is something that concerns you it is best to try and audition first or be able to return it if you don't like it.
Or you know - buy more sensitive speakers so you can buy amps based on sound quality over power quantity.
