We have to discover these differences that raise the price from 100$ for the simple K8n SLI TO 280$ for the platinum one:
1- The Color (LOL) Red (in simple one) and Black ( in Platinum).
2- The Audio Chip is the big difference Becuz the Creative chip is really expensive.
3- Any other difference may be about the package and its contents.
They added a heatpipe to cool the NB/SB.
There's now a dedicated x4 PCI-Express slot.
The upgraded Creative chip you mentioned. Don't short change an upgrade from SB Live! to Audigy. Completely different chips.
It supports dual x16 on the SLI slots.
There's an updated Silicon controller for the SATA connections if you don't use the nVidia supplied controller.
It supports higher voltage on the DIMM slots.
Better RAID support.