(I originally posted this response under a different thread)
I own a Zen Mini Mk3 now for about three months, but have no experience with any other music servers; this is my first.
I am quite pleased with it. I bought the Mini only, no LPS.
Very easily ripped my small 250 CD library; the Innuos OS is very intuitive and friendly feeling to me.
Reasoning that the perfect DC supply for the mini would be a battery (no AC ripple, appearing as a straight-line DC pattern if observed on a scope) I brought in a massive 12V auto battery and hooked it to the Mini. Worked fine, no surprise but, as you can imagine, it was difficult to quickly A/B between the battery and the wall-wart switching supply that came with the unit. I could not hear much difference, perhaps a slight improvement. I measured dc current to the Mini at 250 ma idle, and 350ma with the hard drive spinning. Very easy load for an auto battery.
The Innuos LPS is spec'd to have an output of 16VDC so, knowing that I would NOT be leaving a 12V battery laying around our living room, I picked up a surplus, high-grade industrial, linear, 15VDC power supply. Working beautifully and does sound better than the wall-wart switching supply that came with the Zen.
With regard to a DAC, I used the Zen's built-in DAC for a month or so, Sounds fine. I recently bought a very reasonably priced Chinese made DAC that is quite noticeably better. Had my wife sit while I (blind) A/B'd between the two DAC's and she consistently picked the new DAC as sounding much better.
My system is: Zen Mini Mk3, Counterpoint 3.1 preamp, Cary AES SE-1 300B kit-built amp, all feeding my Klipschorn's, recently upgraded with Greg Roberts/Volti full upgrade package. A completely awesome upgrade, BTW, worth every penny and wish I'd done it ten years ago!
Again, this stuff is all kind of new to me, but I am really happy with my sound.
-Jim