
Off topic but is there any way you can compare the three DACs? Maybe you can PM?
In a thread about DAC's, I wouldn't think it's too off topic. I've done plenty of comparisons of the DAC-19 and Theta Basic II in other threads. The short version is this:
My Theta is balanced and the DAC-19 is SE. When using them both in SE mode, I'm not sure that I'd be able to pick them apart in a blind test, that's how close their sounds are. Balanced, the Theta pulls ahead a bit in soundstage/separation/imaging as you might expect.
Picking one over the other comes down to price vs warranty/dependability/convenience. The Theta is significantly cheaper since it's vintage, but you also run the risk of it dying at any moment. Sure, it's built like a tank, but it's still 20 years old. Oh and you have to deal with finding one. And of course, vintage DAC's don't have USB.
The DAC-19 is much more expensive, but it's brand new, easy to order and comes with a warranty and a USB port. Kingwa is very supportive of all his products and every Audio-GD that I've ever owned has felt like an amazing value for the money.
The Adcom GDA-600 was the cheapest of the three by a mile. Mine was $89 before shipping! It's also vintage with all the drawbacks that come with that and it's single-ended. Sonically, it's similar to the other two, but it's a bit congested with a smaller soundstage and poor separation, especially when compared to the balanced Theta. That said, given the price, it's a spectacular value for anyone looking to get their first "real" DAC or anyone looking to hear what all the R2R hype is about.
As a side bonus, if you're into DIY, there are some upgrades you can do that supposedly really open up the soundstage and beef up the bass. Mainly, we're talking about upgrading the opamps and some caps. I think the total in parts alone was something like $250-300 so it's putting you into Theta territory. I plan on doing the upgrades on mine just for the fun of it. The PCM-63 in the GDA-600 is supposed to be one of the best Burr-Brown R2R chips they made so I believe there is plenty of room for improvement.
I almost picked up the GDA-700 at one point and I'm still curious about how it sounds. It uses a different chip than the 600 and it's fully balanced so I suspect it's more different sounding than one might expect given the model numbers.
That turned into a no-so-short version...