Picked up the loaner and have had a couple days with it and wanted to share my thoughts on it. I won't cover build and aesthetics as I think others have covered that well enough so I'll just get into the sound.
The Soundaware P1 is a surprisingly powerful little amplifier. It has quite a bit of gain in high gain, only letting me getting a short way up the dial with most headphones. Overall I find the P1 has an added sense of body, lending more weight and macrodynamic impact to music. I also find it has a bit of a smoothness to the the sound of the amp which was good for harsher music. The amplifier seems quite powerful, able to drive my HE6 fairly easily, to quite loud levels without sacrificing bass impact as I've found some other amps do. In that pairing I find the additional smoothness and body giving the headphone a slightly softer edge than it usually has. Other aspects of the amp seem quite adequate. I don't any over coloration of tone, the aforementioned qualities keep the amp from sounding too thin or dry which can be typical of a lot of solid state designs, I think Soundaware did a good job of voicing this amplifier to avoid those kinds of issues. The closest comparison to another amp I have around and heard almost immediately was to the amp section of my Audio-gd NFB-27H. I find these amps share a lot of the same qualities sonically and are quite comparable overall. In my listening I did find the soundstage to be of adequate size and somewhat consistent in shape between different music tracks, with the individual sources of sound being fairly well separated from one another. The amp seems to have a decent sense of width and a bit of depth to the soundstage.
Overall I find the amp has a smooth and heavy bodied character with a very black background. I find the smoothness and added body to work well with certain music but doesn't necessarily complement all of it. I have quite enjoyed my time with the amp so far and would like to thank Soundaware for letting me participate in this loaner.