775 boards let you unlink the RAM, but I think with AMD, it is always linked. Bump the voltage up for the RAM, use slightly more relaxed timings (maybe Cas 10 instead of 9), as it will help your overclock. Remember when bumping up the bus, a small bus change will result in a big memory clock speed, which you may mean you drop the RAM to one frequecny below what it is at at the mo when the speed increases.
Going from a base clock of 200 --> 210 made my RAM go from 1600 to 1680, which is a reasonable jump. You may get a hundred or two MHz, but don't expect miracles.
