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It is not possible.

It will neither decode the discs, and even if it did, the G5 uses a digital out for multichannel, while SACD output requires separate 5.1 analog outputs.

However, there are many low cost alternatives to $4000+ audiophile SACD players these days. There is a Pioneer DVD player available at Best Buy that supports SACD multichannel as well as DVD-Audio for about $170.
 
If you want to rip a SACD, there is a workaround. Put the disc in a CDROM drive (not one which reads DVDs) and copy it to a CDR. This works for most SACDs as they have a CD layer too. Your Mac will see the CDR normally, but sees the SACD as a blank DVD.
 
Are SACDs DVDs, or or they a different type of media? If they are DVDs, then it will probably just be a matter of time before someone comes out with a player.
 
There are 2 types of SACD discs:

1. Standard SACD. Plays only on SACD players.

2. Hybrid SACD. The platter or disc itself has two layers: a standard Redbook CD and a buried SACD layer. This disc is playable on both CD and SACD players.

SACD, being a very high resolution format, sits on a DVD-type layer (4.7GB), but the format is proprietary and encrypted. After lengthy deliberations, a digital audio output format is finally ready, but found only in the high-end SACD players. Sony is particularly concerned about piracy, so it's doubtful whether they have any plans to make SACDs readable on a computer (i.e. SACD-capable drives) or even to license the digital audio output format for use by software/OS companies.
 
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