Kevin, my bad...I totally forgot the Ack is battery powered. :)
but, before you go the upgrade path, I think the dynamics, in case of your system, could be improved simply by upgrading a digital cable.
Digital cables make a big difference. The cable you're using may not be best choice. I recently tried Virtual Dynamics digital cables and the improvement I heard was amazing. I don't know how much you wanted to spend on the upgrade of the dac, but why don't you try a Virtual Dynamics NiteII or Master digital cables. Just borrow them from cable company. You won't beleive the sound.
What you're looking for is easily achived with Virtual Dynamics Master digital interconnect. NiteII is great also, but Master excells at speed and dynamics. NiteII will give you a very smooth, very analog sound with trememndous bass extension. Master will give you all that the NiteII does, but with much greater resolution, speed and dynamic drive.
I listen to rock and blues as well and my Bel Canto DAC2 with the VD Master cable was able to reproduce the recording like I have never heard before.
These cables are expensive(that's why I am suggesting you borrow them first from cable company) but the level of performance your system will achieve will be way beyond what you expected.
On a side note, replacing Flavor2 with Audience powerChord may boost the dynamic drive of the amplifier noticibly.
Anyway, whatever you decide, best of luck.
