Hi Jan, thanks for responding...
I appologize to the community for distracting you from your vital work on the Porta Corda.
I had assumed that the reason for the minis was due to the fact that most phones now come with the mini and an adapter. I hadn't thought of the possibility of yanking the amp off the shelf. Good call.
Believe me, I have considered soldering the cable directly to the board. This is actually feasible with the HD-600s, since the cable easily unplugs from the headset. Don't cringe like that, I would run the cable out the back panel with proper strain relief.
Another alternative for me is to add a panel mounted jack to the back of the unit. I agree that the 1/4" plug is less than ideal, but it is pretty common. It is also what occupies the upstream end of my HD-600s. I clipped off the bad mini that came on them and replaced it with a 1/4". As you said, one less interface.
Right now I am leaning toward the Corda kit for the 600s at work, and an SAC for the K1000s at home. How convenient, since you sell both!
Always the quest!