Because I just got myself a stepped attenuator, I wanted to hear how my SN3 sounded as a power amp only.
So I connected the passive volume control to the AV RCA input.
I used my streamer as source.
In short, the power amp alone sounds ”fatter”, than SN3 as an integrated.
Most here went from SN3 to 282/hicap/ SN3 power amp, then 282/250.
Plenty of posts here on that.
Yes, I know. I just wanted to know how it sounds as a power amp. I also have a Hicap DR.
The Hicap DR only powers the preamp side. 
I know.
I assume you were using the AV input in “bypass” mode for this test? My understanding is that it only bypasses the volume control so is still running the signal through some/most of the preamp circuits.
It would be an interesting experiment to run the SN3 in normal mode with its volume set to midway and your passive volume control setting the level.
I originally had a SN3 and HCDR in my main system and also tried the SN3 in power amp mode only. Tried it using a NAD C658 Streamer/DAC/PreAmp and later a Lumin P1 Streamer/DAC/PreAmp and neither sounded anywhere near as good than using their fixed outputs into a normal line in on the SN3 thus using the SN3 as a full integrated amp.
The AV Bypass option is really only any good for taking an AV Amp PreAmp signal as its not so critical sound quality wise for movies etc.
Interesting. Have you tried the SN3 with something like a 282? This is something i’m curious about. Or even a NAC 333 
Unfortunately, I dont have unlimited access to loads of different hifi equipment to try with the SN3 in Power Amp mode, so no, I have not tried a 282 or a 333 or is it a 332.
I currently use a Lumin P1 Mini Streamer/DAC/PreAmp into my SN3, but Im not using the PreAmp functionality as my previous experience with PreAmps into SN3 in Power Amp mode was poor, so Im using the P1 Mini in fixed output mode into the streamer input of the SN3 and it sounds very good.
There is only so much testing you can do, or is worth doing.