Now that the dust has settled a little I have had time to rethink the mod wiring.
The latest suggestion for trying out the mod requires only two pieces of wires. That means that you can try the mod out before deciding if you want to invest in two expensive caps.
Remove the line output opamp.
Solder two pieces of wires to the outer pins on the connector on the left side of the PCB (looking at the DAC from the front).
Push the bare ends of the left wire into pin 1 of the empty IC socket.
Push the bare ends of the rightt wire into pin 7 of the empty IC socket.
This way of doing it allows you to also add some improvements to the headphone section. The muting circuit is also fully functional, and there is a bit of HF filtering to remove some of any HF noise.
If you add the 68nF caps mod ( reddish caps in the picture) by replacing the 100nF ones (blue or yellow on the original PCB), the headphone amp performance will be almost indistinguishable from the original layout. With the THS4032, and some non-polarised caps I am trying out, my HD800 and D7000 have not pulled away significantly from my K701 and HD650 in terms of musicality, detail, and clarity. So for headphone users this alternative way of adding the mod is well worth a go.