Currently using Audinst HUD MX1 + AKG Q701. Can't decide whether to invest into HE-400. My Q701s are a bit bass shy and a tad bit bright so I was hoping HE-400 would fix that but looks like many people consider HE-400 harsh, sibiliant, and tizzy which is not a good trait for a 400$ pair of headphones. Any truth to that? Perhaps HD650 will be a better investment.
I'd say HE400 is tizzy (things sound more sparkly than natural, emphasis in upper treble), but not sibilant ("ssss", emphasis in low ~ mid-treble) or harsh (usually due to uneven peaks in treble,rather than a particular band of emphasis). If you can't tolerate treble energy then HD650 will indeed be a better investment.