Injecting one sub to Benchmark system…

The idea behind running the headphone out for the sub is that having the pre-outs running two sets of wires at the same time and into 2 amplifiers at the same time is harder for the dac to power than a single set of wires and amp.  Running from the headphone amp to the sub would, I think, reduce that because the headphone amp is its own separate amplification from the preouts.  And it's something you can try for the cost of a $5 headphone jack to rca adapter.  

IMO it's a mistake to not try a regular preamp with the Benchmarks.  While there may be a tiny loss of transparency I found a preamp was overall a pretty big improvement.

@m-db 

This is exactly what I did.  

@jon_5912,

Your last paragraph is perfection!

You’ve now mentioned “twice” (or has it been once) using headphone output. Funny, for I’ve also done such configuration on an older Vintage piece of gear which had no pre-out. Receiver > Amp. What can I say other than I love my tone controls, and desired to still utilize them with the added headroom. Likely somewhat of a impedance mismatch but hey, it worked.

;-)