I guess I don't have that already written...... I was thinking about the DSS2 + PC360 setup to use chat, and not the nasty "voice though speakers" method.
The setup to use two amps, the DSS2 and the Mixamp, is pretty simple. Toslink optical from the 360 to the DSS2. Then use a 3.5mm to 3.5mm male cable to go from the DSS2 output (where you'd normally plug in headphones) to the Mixamp MP3input. Not the other input.
On the mixamp, disable the dolby digital, and you can turn the voice all the way up, and use the volume on that just for the voice, and use the volume on the DSS2 just for the game audio.
The PC360 plug into the mixamp like you normally would. Chat cable from the Mixamp to the 360 controller. Also works with PC and PS3, if you have the PS3 chat cable with the mixamp.
For the 3.5mm patch cable, I recommend this one, or a similar short and think cable for minimal additional noise:
I've seen other setups where people use a mixer as an amp... And I've tried using a FiiO7 inline headset amp booster to boost the chat volume and overall volume... but the FiiO7 doesn't compare to this setup, and the FiiO7 is similar price to the DSS2 anyways.
The DSS2 really has the power to fill nice headphones. Even with the new Astro Mixamp that has a seperate amp for voice and game, it doesn't compare.
And with this setup, I prefer the OLD ASTRO MIXAMPS, NOT THE 2013 VERSIONS. The new ones have a little too much extra noise. --- There's no sensation to compare with this Suspended animation, a state of bliss