OCC has published a new review on the Gigabyte X48T-DQ6

Overclocking the X48T-DQ6 was in all respects just the same as the X48-DQ6. The Q9450 I use in my reviews ran up on the same 470FSB limit that it did on the DDR2 version of the board. This limited my memory overclock to only 940MHz at 8-8-8-24 1t. Tweaking the voltages and timings did not allow me to progress any further. Reaching the limits of my chip may seem like a bad thing, but it's not really when you look at it. Some never get that far, while some people can eclipse the results I have achieved. It all comes down to how good your individual hardware is and the time it takes to pull the most from the X48T-DQ6. There are enough options in the BIOS to allow for fine tuning the voltages, clockspeeds and memory dividers. I found that the B (333) dividers were the most stable for the hardware I used on this board. Of course, your mileage may vary.

Gigabyte X48T-DQ6 Review