is there a reason why you're wanting powered speakers and a dac instead of passive speakers with a receiver? passive speakers would give you quite a bit more choice in terms of bookshelves.
the schiit is a good 2.0 dac. not much to be said besides that. its half the price of a low end receiver though which would pair well with entry level bookshelves so unless you really want to go the powered route and a small dac [if you have very little space for instance] it may make more sense to go passive with an amp/receiver.
not sure about the a5 but i know the a2 is very fussy with placement and i would not expect much bass out of them. no experience with kef.
Honestly, I would prefer to have an all in one powered speaker - speaker/amp/dac. The reason for me is simple - it's not my main audio system (I already have one in a separate room), and it's not my home theatre system (have one of those, too). I want something that's good, but not where I am needing to buy all these components and turning it into a miniature version of the two systems I already have. Just something that I can enjoy music and movies from when I am in my office all day working.
The KEF is an all in one. The A5+s would need a DAC, and the Schist Modi 2 is cheap and good (especially for this specific set-up). So that's about as much gear as I would want to buy for a casual, while working set-up. I don't want to have to dig into passive speakers, amp, pre and dac - it's way overkill for something that is NOT a primary system.
I've listened to the R100 (which is passive) which should be rather similar to the X300A's and liked them better than the A5+'s, overall I believe it gives you a better soundstage. That and the fact that you want a simple setup, it just seems like it would be the best way to go.
At that price range I would also consider the Paradigm A2 Shift powered speakers. http/www.paradigm.com/products-current/model=a2/page=overview
You would need the Schiit volume control with the KEF or Paradigm since the DAC doesn't have variable out the way a PC would. It's better to have separate components in the long run so you can upgrade the weakest one to improve the sound quality.