That's the wave of the future. With processors coming out today, ie the PPC 970 from IBM, able to use up to 2+ Terabytes of RAM, it's almost mind boggling. Although, it will be too much for a desktop to be able to handle (how many watts of power would that take?) today, maybe in ten years this will be the norm. Although, we'll have to leave the world of current 32 bit processors to acheive RAM limits of 1000/GB's, I see that happening soon too.
What's the power consumption of the Opteron? Compared to the P4? I know PPC runs relatively cool compared to x86, but I don't really know anything about the Opteron's power consumption.