I have done some reading, and found that both of these products received good reviews, and had features that I like. My budget, unfortunately, is a bit smaller than I would have liked, so my max would be around $1200 for a DAC and an amplifier. Ideally, I would like to keep it under $1000, but I realize that head-fi isn't the best way to save my wallet. ;)
I like the fact that the Stagedac can also function as a preamp, in case I choose to use it with a speaker setup, and I also think I would enjoy the crossfeed settings very much, along with the significantly superior digital to analog conversion. I also had a chance to try my HD595s with a Woo Audio 6 earlier this year at a headphone meet, and found the pairing to be quite pleasant.
I realize it might be a bit silly to spend $1200 in electronics for a pair of $200 headphones, but I am trying to avoid a piecemeal upgrade path (for example, purchasing a 0404 USB, then upgrading later, instead of doing it 'right' the first time). If I ever did choose to upgrade my headphones, however, I very much enjoyed the sound of the HD650s when I demo'd them. I have used the HD595s with a ZERO DAC/amp in the past, which I sold due to the persistent smell of rubber coming from the unit, if that provides any insight in to the audio 'jump forward' I am attempting to make.
Essentially, I'm hoping for some alternate suggestions that might bring my audio expenditures under control, and failing that, advice on how well the Stagedac and the Woo Audio 3 will pair up. I would like to apologize in advance for my poor English, and, additionally, offer my thanks in advance to anyone who chooses to help!