Best power match with Sonus Extrema ?

I am looking for the best power to my new Extremas.
I use PSAudio PWDII and a Macintosh c2200 pre.
I would like to get the most neutral and detailed sound
I tried a few big "names" (Krell, ML, Manley) - no success.
Please let me know your advice.

Thanks,

Amnon