I see a problem here. P35 is not able to run the memory slower than the FSB so at stock speed with 1333FSB (it's quad-pumped so 4 x 333) you are already running the DDR2 at least at 333MHz. If that "300MHz" PQI is only DDR2-667 then you'd probably have to either remove it or considerably raise the voltage or lower timings to get it to run at the standard 400MHz of DDR2-800 needed to run at the usual 1600MHz FSB used by Extreme processors.
At 1600, 8 x 400 = 3.2GHz from your E6750 which should only require a minor bump in voltage. Figure on about 68w of actual CPU power consumption, up from the 50w actual of stock (yes, these used much less than their rated 65w TDP, a concept foreign to the Intel of today), which should be pretty warm on the stock cooler but acceptable. It's a pretty unimpressive 500MHz overclock because the stock FSB is too high (better to start with a 800 or 1066 FSB chip if you wish to overclock since those will have higher multipliers) but this is exactly what allows for overclocking on a stock cooler. After all the cooler was designed to handle 65w TDP.
If your GT730 is a Kepler instead of Fermi, then it should overclock like crazy, like +350MHz. If it's Fermi then you would quickly run into the 75w power limit since even at the stock 700MHz it's already at double the wattage of the Kepler at 49w.