Looking for an upgrade to my Ack Dack 2.0

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.

Gongos, that is good to know. I sent an email to Steve last night and he said the dynamics could definitely be improved. Also, RAM does mods to the Ack as well.

I am not wedded to the Ack per se, but I like its tone (rich and full), but I want to see if I can have something that takes this tone but adds more speed and impact. I listen to rock and blues music a lot and impact is important to me.

My system consists of a modified Squeezebox 2, using a Bolder Cable digital cable to the Ack Dack, going into a Singlepower Supra tubed headphone amp, and finally my Grado RS-1s. Power cord on the amp is a Venhaus Flavor 2. Ack is obviously battery powered.

I am not sure I have a problem. It is hard to tell without listening to a DAC known for great dynamics (but still possesing a rich tone). I did notice when I used 5687 tubes as outputs in my amp (via adapters) I got a lot more impact with my music (previously I was using 12sn7 tubes).

It's just a feeling that my Ack is not as dynamic as it could be. It may be a totally false assumption, but I want to consider other options, with modding the Ack being one of them.

what transport and digital cable you are using? What is the power cord on the amp, dac and transport?
What headphones?

If you list the associated equipment and your music choice it would be easier to pin the problem.

I compared the Modded unit to a 1.x. I talked to Steve before I sent in the Dack, and he told me it didn't make a difference if I sent in a 2.0 or a 1.x--the end results would be the same. The modded unit was much better from top to bottom. The most obvious improvements were more detail, dynamics, and an amazing 3-D presentation.

I'd imagine the results of modding your 2.0 would be similar. Or, you could sell the 2.0, buy a cheaper 1.x, and have the 1.x sent in for mods.

Gongos, did you compare a modded Ack 2.0 or the 1.x model? If so, what improvements did you notice?

Get the Ack modified by empiricalaudio.com. I a/b'd between a stock model and a modded one--no contest.

I don't have it hooked up to any preamp. It goes directly into my tubed headphone amp. I appreciate the advice, but I don't really want to have to assemble anything. My time and skills are pretty limited.

What do you hook your DAC to, a passive or active preamp? This may make it easier to narrow down the choices. If using an active preamp with a decent input impedance,I recommend listening to the Audio Sector Dac. I think it will give you what your looking for. You can get the Premium gold kit for around $250 or you maybe able to sweet talk Peter into building you one in a simple non-chassis for $350.This little DAC uses a 48 volt 6 amp transformer that outputs 8 volts to the digital side and a separate 8 volts to the analog side. It is a very very dynamic little DAC. I think you'll be very surprised with what you get for spending less. What ever Peter builds..he gives a money back guarantee with a lifetime warranty. Can't beat that with a stick. Not a cheerleader for the company..just a happy customer.;-)

Good luck!