After searching the head-fi for combination and opamp orders...
my current second best for the P4 is AD8599 (class A)+ HA-5002(Buffer) + ISL 55002 (G/V)
Edit: After few hours of listening, I changed LT1355 in place of ad8599, this bring the sound stage closer to listener. I think this is the best now.
You might give the LT1678 a try in place of the LT1355. IMO, it is better balanced across the audio spectrum and imparts a greater sense of realism.
I also prefer a dummy adapter in the center ground channel.