OPA is based on IC, therefore it has bad quality inside as well mentioned here:
Once you compare OPAs with discrete components (I did) there is no turning back.
I tested a lot OPAs with discrete components before (while doing Xonar STX mod), and the one to sound terrible was always with OPAs. Did you really compared (heard) them?
And no, I'm not planning to use Burson for this project.
You call "DIY standard" as something bad and not for "commercial devices", but keep in mind the very same USB to I2S used on DA8 did come from DIY:
I know test equipment costs a lot, but you can always rent them for a project or two, or buying 2nd hand (sometimes can saves a lot).
I think you're passing judgement off narrow experience. First, the Asus STX is hardly the last say in opamps vs. discrete, and varies from application. Second, you have the term "DIY Standard" misunderstood. Commercial goes through much, much more testing and R&D than DIY. There are licenses, bills, employees, equipment, advertising etc. to pay off too. It's also not about using a component that is available through "DIY channels", nearly everything is. If you want to build an equivalent DAC to the DA8 in your own home for $700, then good luck, but please stop complaining about a product that is well-designed, and excellent SQ, without even owning it. Thanks.