Preamp with most dynamic contrast?

Which preamp in the $ 2000 to $ 5000 range offers the most dynamic contrast (both macro and micro)?

My current set up offers what I value most in spades (no listener fatigue, true timber and great imaging) but is somewhat mellow in dynamic contrasts, especially Micro. I think a change in preamps might do the trick. Current system: Vienna Accoustic Mahler speakers, Bryston 4BST amp, Electrocompaniet EC 4.7 preamp, Meridian 508.24 CD run balanced.
PS: I am tempted to try tubes this time...thanks in advance for your kind suggestions.

Bruno