or do i need a receiver/amp that has a "Dolby headphone' or similar tech to decode the signal first?
I've seen anecdotal evidence which suggests that if you use something like the su-dh1, it should work.
I'll be testing it out very soon myself...
WATSUI earlier in this thread confirmed that the Mixamp + RS180 works nicely for him.
So it's quite likely the same would be true for the SU-DH1...