Hi Okamoto, Here are some of my impressions.
Generally, the HA-160 is a quite warm piece of solid state, so it produces a non-fatiguing sound. Mids are lovely, imaging is nice, bass is solid but the HA-160 sounds relatively forward.
I compared HE5-LE and HE-500 using the Burson HA-160 and the Auditor, and I think the HE-5LE pairs very nicely with the HA-160. The HE-500 works as well, but the sound really is forward, since both - amp and phones - are forward sounding. Differences are more pronounced with the HE-5LE than with the HE-500 and (because?) the HE-5LE seems more difficult to drive. The Burson delivers more bass with the HE5-LE, and to a lesser extend also with the HE-500. One difference between the amps listening to the HE-500 would be that the Burson sounds lesser grainy. The treble is smooth but not rolled off, mids are almost tubey and the bass is nicely satisfactory to my ears. Although the sound is smooth, it still sounds clear and very detailed. This is why the imaging also works pretty well. So, if you don't mind a quite forward presentation, you can have this one on your short list. Works for me. IMHO and YMMV.
PS: I have got the HE-5LE and HA-160 on loan.
You think the HE-500 is forward sounding?