I am driving the Abyss Phi with XI Audio Formula S + Powerman external power supply. What I can say is that the 2W Formula S (in high gain mode, i.e. +16dB) drives the Abyss with plenty of authority and grunt, combined with a finesse, transparency and tonal balance which closely match driving them through DAVE alone.
I can easily reach realistic SPL even on very low level classical recordings of very large orchestral pieces, with a visceral impact which effectively mimics a live experience (OK, not quite there, but as close as a headphone rig can get) with no audible distortion, compression or clipping. Extreme dynamic pieces with demanding sub-bass passages - like organ tracks - exhibit a skull rattling rumble which is an experience in itself.
This was not possible with DAVE alone, but I would say DAVE is able to squeeze a more than decent amount of quality AND quantity from the Abyss in 80-90% of cases for my tastes and my musical preferences / typical listening levels (more about DAVE direct vs. DAVE + XI Audio amp here: https://www.head-fi.org/threads/chord-electronics-dave.766517/page-782#post-14394739).
As for the recessed mids issue, the Phi CC pads are able to give the vocals more focus, presence and tactility IMHO, and with the benefit of the DAVE crossfeed function, I can "see" the singer / soloist just before me and in front of the other musicians, pretty much where I would expect them to be
I can easily reach realistic SPL even on very low level classical recordings of very large orchestral pieces, with a visceral impact which effectively mimics a live experience (OK, not quite there, but as close as a headphone rig can get) with no audible distortion, compression or clipping. Extreme dynamic pieces with demanding sub-bass passages - like organ tracks - exhibit a skull rattling rumble which is an experience in itself.
This was not possible with DAVE alone, but I would say DAVE is able to squeeze a more than decent amount of quality AND quantity from the Abyss in 80-90% of cases for my tastes and my musical preferences / typical listening levels (more about DAVE direct vs. DAVE + XI Audio amp here: https://www.head-fi.org/threads/chord-electronics-dave.766517/page-782#post-14394739).
As for the recessed mids issue, the Phi CC pads are able to give the vocals more focus, presence and tactility IMHO, and with the benefit of the DAVE crossfeed function, I can "see" the singer / soloist just before me and in front of the other musicians, pretty much where I would expect them to be