what i meant earlier with regards beebman was some external AD/DA , perhaps from Apogee, or RME, ( see the rosetta 200 as an example )
this would provide 2 channels in and out of very high quality audio.... without the need to use an actual interface as such... simply using the G5's onboard SPDIF.
some people might have things like that already, and may not have considered using it in that manner,
as a cheaper version one could use a DAT or CDR or MD recorder as external AD/DA
it would work... but the quality is variable....
if you don't know who i am, i aint gonna tell you.