As far as I remember reading, the 598 decodes DD and DTS and converts it to multichannel PCM 24 bit. The 568.2mm via smartlink only then takes each channel and upsamples it from 48k to 96k. 2 channel PCM input only via SPDIF is also upsampled in all channels in the 568.2. DD and DTS via SPDIF is not converted to 24bit, 96k in the 568.2. I find the difference quite noticable. Upsampled movie sound is noticably better. More dynamic, smoother and more natural sounding. More depth of image. Especially DTS upsampled. WOW! Using the SPDIF input still sounds very good...your not losing a lot but it does sound noticably better via smartlink in my system when watching movies. But remember its movies so I probably wouldn't miss it a whole lot if my 598 died. My 596 would be just fine and CD's will be just as good.

Ron

HT: 568.2mm (Revelation One filter), 518x2, SB3, Bryston 7BSTx3, 8BST, Aerial 10T, CC3, SW12(Qty2) w/SVS AS-EQ1, MK Tripole x4. JVC RS1u, DVDO Duo, Oppo 103 w/Vanity103HD, Sony PS3, VIP 3D Theatre, Acer H5360. Logitech Ultimate Remote and Hub.