HDMI or SPDIF/TOSLINK

[chimar]

On a source such as a SKY HD box for audio out (say BBC Radio 3) would you get a better audio output in this order?

a) SPDIF (coax)
b) Toslink (optical)
c) HDMI

I am thinking of this going into something like an AV amp?

Also in terms of distance am I correct that with good quality cables you could get 15 to 20m with a/b/c or is there is a difference between them in terms of single quality loss?

My thinking here is about adding more Sekrit DSi and rack .v. local room location.