"...but I've heard that passives are much less dynamic than active preamps..."
Where do these strange "rumors" come from? Preamp manufacturers??
The absolute BEST, ANY preamp can do, is leave the signal unadulterated, while only acting as a "wire with gain".
I owned several "big gun" ($8 - $10k) preamps before finally going with a passive preamp with my BAT P10 phono stage. It was BY FAR much more transparent, with NO loss of dynamics or "headroom".
Patrick, if your looking for the purest, cleanest signal possible (unless you can afford a $10k preamp) at least TRY a passive pre with your set up.
The only possible downside will be one of gain (as in not enough of) depending on the cartridge and phono stage output used.
Good luck!