It's 4.7 a side, some burners can do both which is 9.4.

I think I quite like the sound of this. However the main concerns are cost, 160Gb worth of discs (at £15-20 per disc) would cost close to £600 + £600 (cost of the drive). Ouch! Price aside the other thing is I tend to just drag and drop all my wav's onto lame to batch encode them (fyi this takes 3-4 days), and leave the PC to do it's thing. With 4.7Gb per disc, I would have to make frequent visits every so often to keep on feeding the encoder.