Have you considered using a line selector + headphone amp? Like the
Coleman Audio LS3 or Niles AXP-1. Both of those have RCA
(unbalanced) connectors, but would the trick. The Hosa SLW-333 has
TRS balanced, 3 in, 1 out.
I've read good things about the Presonus HP4 (I think that's the
name), but it's only 1 in, 1 out (stereo).