No contest. Take the Classe. The Adcom is over hyped and overrated in my opinion. I had one and the passive section killed the dynamics in my system (which some other passives didn't do including the McCormack TLC-1, Placette Passive, and even the inexpensive Creek OBH-12).
On the other hand, in active mode the GFP-750 was nothing special... a bit too cold and lean sounding for my taste.