Sapphire 5850 Xtreme @ Stock Voltage, 1000,300MHz
this is one extremely lucky boy

Now that's what I'm talking about! Very nice!
Can you increase the RAM speed a little without losing stability? If so you might score another MH/s. I'm thinking around 350-360 MHz.
With lots of tweaking and testing the best I've gotten from a 1000MHz Sapphire 5850 Xtreme @ stock voltage is 413.3 MH/s (fluctuating between 413.1 and 413.5). If you can beat that then please let me know for some BTC.
Can you push the core clock any higher than 1000 MHz? Are you bound by Trixx or by stability?