Regarding the upcoming JH Audio JH-3A....
You should definitely work with Matt Macbeth with Cypher Labs / GR9 Technologies. He's the one that's developing the DSP Active Crossover Amplifier for the JH-3A. Since it's more than just an amp, it will likely require extensive modifications to the existing HM-801 layout, as it has a digital volume controller and digital control of bass levels. Also the headphone connector is completely different for the JH-3A, it's an 8 pin circular DIN connector.
Another one would be integrating the HeadAmp Pico Slim into the HM-801. But like the JH-3A, it presents the problem of digital volume control. The Pot could be directly wired to, but again, would be a semi-permanent mod and not a simple Gan-Qi card swap.
One way to address these volume control issues would be to have a new Gan-Qi metal cover. With the JH-3A version, it could have those two toggle dials protruding out the back, inside slots cut out of the rear.
The Pico Slim version could have a single opening for a rotary pot. But I think going with a semi-permanent mod of having the pot directly wired would be much better.
Overall, I think an internal Pico Slim would be the "easiest" of all the proposed amp modules, as it does not require a new headphone output socket, unlike a Balanced output or 6 Channel JH Audio output.
Edited by Edwood - 6/10/10 at 2:40pm