Is there any aftermarket cable maker who makes HE-6 cables with speaker taps?

someone doesn't know how to speaker amp the HE-6

build a robinette box (a guide is available on head-fi) if you're DIY-oriented, or buy HFM's speaker amp box (HE-Adapter)
http://www.amazon.com/dp/B00ARIAGTA/

Don't built the robinette box... a design that lets you tie the grounds together with a flip of a switch is just begging for somebody to blow an amp.

Just get a 4-pin XLR (female) and 4 wires. Connect as follows:
pin1 = L+
pin2 = L-
pin3 = R+
pin4 = R-

Do braiding or add bananas or spades or whatever you wish afterwards.

yes, just plug a 50 ohm transducer into something designed to handle 8 ohms, that'll go swimmingly

that definitely won't push the amp way too hard and cause it to distort

A 50 ohm load should be no problem for a solid state amplifier. The only niggle I can think of is if it's a class D output stage that relies on the load to filter out some of the ultrasonic garbage, which still shouldn't be an issue as we are within an order of magnitude of the intended design. Otherwise, a high impedance load should be an easier load as it draws less current and if it's a class A design you'll probably stay within that region longer.

Ah where were you who I did this? Been there, done that and blew out the amp's audio transistors

I got in many fights with robrob over the design of his box as well as many of his other projects. I pointed out the dangers of the design, and offered several very simple fixes (literally snipping a single wire in one case) that would have vastly increased the safety of the device. He shut me down on all of them and refused to admit any danger and that people should know when to flip the switch. Yeah no, that's just laziness and pride getting in the way of safety.

He built entire webpages and apps to help people make calculations etc when he literally only learned the formulas the week before. I can sorta understand the desire to help and he was obviously excited to share, but cripes I was fixing a lot of his errors along the way. He didn't even understand the math behind a resistor divider for Grod's sake, then had the audacity to name the circuit after himself.

Then there was the whole mess with Brunk who rode the hype for the robinette box and stole a ton of money from people. Ugh.