I don't buy the all digital front end argument. I've heard several non fatiguing all digital, computer-audio-based front ends, including my own that sound fantastic. The highs in my system I would describe as crystalline, extended, natural, sweet. Far from forward, harsh, edgy or fatiguing.
The suggestions about speaker and cable synergies and room treatment strike me as the most informed guesses.
The suggestions about speaker and cable synergies and room treatment strike me as the most informed guesses.