A point that should be noted is that the input impedance of the OP's MA-6600 integrated amp is a low 20K for both its balanced and unbalanced inputs. That is marginal at best for use with the Rhea (see the second paragraph here), and I believe also for use with the Herron (ask Keith Herron to be sure, if the VTPH-2 is considered).
Regards,
-- Al
Regards,
-- Al