I think this whole thing needs to be rethought.
First, why bother with SDHC? It can't really hold everyone's DVD collection in full quality anyway. Replace it with 1 TB of RAID 5-configured HDDs.
Also, get rid of the OMAP SoC. Why use such a limited architecture when you could use the CELL processor? Now that's what I'm talking about. B)
Of course, now you've got to consider memory bandwidth in conjunction with high-end hardware, so I think we should shoot for 8 GB of DDR3. I guess 4 GB would be acceptable if the power requirements of 8 GB are too high, though.
As for graphics, well, you can hardly go wrong with the Geforce 9800 X2 - after all, 2 GPUs have to be better than one.
I don't know about everyone else, but I'd be willing to pay a bit more for a device like this.
We could call it PANDORA HEAVY - car battery sold separately.