The Tannoy DMT15 II has higher power handling and sensitivity than the Ardens, so would be better suited to high sound output levels and at 98db sensitivity will go very loud!! Probably more than enough for a barn. I wouldn't mix speaker types and paralleling 8 ohm speakers by using two pairs will give a nominal 4 ohm load and it may be unwise to go below that.
Rather than use a Krell KSA 100, I'd save money and get a big Quad amp like a 909 or QSP, which have bags of power and sound just fine at high outputs, they have output protection too. The Krell may not be too happy delivering sustained high levels the Quads are likely to be more robust. The Quads sound very good with Tannoys.
It is impossible for anything digital to sound analogue, because it isn't analogue!