Just a quick update with about 120 hours on the LC. I'm using my Hifiman HE-400i's, single-ended. I do not have a balanced cable, mostly because I did not expect that much of a difference. However, I have compared the single ended output of my Benchmark DAC-1 to the balanced output. Contrary to what I first reported, and contrary to what I was advised, there is a significant difference in output. The most striking is the volume difference between SE/Balanced out of the DAC-1. I have not taken any measurements at all, and don't have any way to accurately do so. However, my best guess is a 6 dB difference between the outputs of the dac. I really didn't expect this.
But what really blows me away is the sound of the LC versus the headphone output of the Benchmark. The Benchmark is every bit as screechy and glaring as I have ever read it to be. It has a very pronounced treble, and by all accounts it is a very bright amplifier. It does have a lot of detail though, and with moderate listening levels I don't find it too bad. But the LC matches it in detail, and utterly trounces it in terms of bass, soundstage, and generally sounding awesome. I've used the 400i's on a few amps, including the headphone output of my iPhone, and always thought they sounded great regardless of amplification. This might be true, but even in single ended mode, the LC is nothing short of astounding at eking out a whole other level of performance from my favorite headphones.
Interestingly, the LC doesn't sound that great using my Grado SR-225i's, which I usually enjoy listening to. I may have had too high of expectations, but the Grado's still sounded exactly like Grado's, and the difference between the LC and the Benchmark weren't that great. It was a little disappointing.
But the sound I'm getting out of the 400i's more than makes up for everything. I still feel strange preferring them to my Alpha Primes, but with most material I certainly do. The LC simply makes me prefer the 400i's even more!