Yeah I recently read that too, in an old review of the 170's. I have yet to read anyone directly comparing the HSU and the Rythmik, and I've looked. Just lots of "The Rythmik is awesome. And the HSU is also great." My OCD would nag me mightily about getting whichever one was incrementally better. I'm like that with black levels too.
But I do distinctly remember when first using my HSU, I was watching the beginning of Transformers: Dark of the Moon, the part on Cybertron where they showed the inside of a ship while they were firing giant bullets (rrgh, how come they never used lasers in that whole movie series? Cause they don't make explode enough, duh!) anyway, when the shells were hitting the ground, the very deep clanging of them bouncing off the ship's hull was incredibly detailed, and immensely satisfying to behold (much moreso than those drab and convoluted robot designs). Something my BIC H-100, which I loved, didn't render nearly as well.
In fact, I've decided to mux out that exact clip (with 1536 kbps DTS audio), and upload it so y'all can test it on your own equipment and see what you think: Transformers ClipEdited by lexlynx - 7/1/13 at 11:14pm