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, straight-line DC if observed on a scope. So 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. I measured dc current to the Mini at 250 ma idle, and 350 ma with the, I believe, it's 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 the 12V battery laying around our living room, I have opted to a used high-grade industrial linear 15VDC power supply. Working beautifully.
With regard to iPeng, I like it. Again, I have no other experience with music servers or associated control apps, so please keep that in mind. We are iPhone/Mac users so it felt right at home. I doubt I am using all the features of iPeng, but am still learning. Easy to make a Favorites playlist.
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 SE 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!
Trip, again, this stuff is all kind of new to me, but I am really happy with my sound.