Hey guys,
Update: I got a nice active pre (Audio Refinement Pre 5) to play around with. Kazam! No problem blasting the system loud enough to peel paint. However, I found the whole sound shifted dramatically. Even the PRAT -- with the Creek passive, I was getting sort of laid back sound - the system now sounds faster, more urgent. The sound is tighter overall, more dynamic (surprise, surprise), but initially, it was unbearably aggressive to my ears, a little white and flat-sounding, very solid state-ish. So I went to fooling around with cables and tubes. Found out the biggest culprit was the Russian-made 12bh7s in the Anthem (follow the Amperex 12ax7). With the Creek the Electro Harmonix 12bh7s gave me more drive and a clearer, cleaner sound than the NOS tubes I had, but with the AR in the chain they're overkill. Swapped 'em out for some NOS Sylvania 12bh7s and the sound is quite good -- it has the richness, depth and nonfatiguing quality of the Creek, but with more slam and higher SPLs.
I still feel like I'm missing some of the depth I had with the passive setup, though. Now I'm eyeing the stock power cords on the AR and my Muse DAC. And thinking about getting different NOS 12bh7s to roll into the Anthem. Damn this hobby and its infinitely forking paths to nirvana/neurosis!