I too have been struggling to find the "right" synergy with the de capo i's. I've auditioned the Plinius 8100 (open, clear, black background, but glassy on top, particularly when pushed), the Classe CAP-151 (smooth, dynamic, but cool), the Rogue Tempest Magnum (nice, but not enough clarity) and the Sim I-3 (dynamic, but not as black as the Plinius). I settled on the Sim I-5 (more refined than the I-3). However, after living with the I-5 for a while, I'm still looking for a little more warmth and body (particularly in the low end). I recently auditioned the Audiomat Arpege Reference (all the warmth and body that you could want, but slightly veiled) and it's bigger brother the Prelude (leaner, quicker). The Prelude Reference may be the best of the group so far; very musical, detailed, but not fatiguing. I just wish it came in black (WAF)!
Good luck!
Good luck!