Ok... due to everyone pushing me to push the chip a little bit further, I'm now running the chip at 4Ghz @ 1.3V. I'm using Orthos to verify its stability right now. I've also pushed the memory to 890mhz @ 2.1V (5-5-5-15)
BTW, the chip is an E0 stepping. I assume that's a good thing for us.
EDIT: it's been running Orthos for 10 minutes now, so this looks promising.