OCC has published a new review on the Sapphire HD4670

This version of the HD4670 was much more overclocking friendly that the Powercolor version I tested. Whereas that card did not want to give up any additional clock speed, the Sapphire version easily eclipsed the marks set by that card. The memory on this card just kept scaling upwards and finally gave up the ghost at 1070MHz. I backed down the clock speed 5MHz and I was ready to go. The Core speed increase was not all that substantial, but it is easily 15MHz faster than the Powercolor card. With this additional clock speed, there should be an increase in the performance delivered without a big noise penalty as the fan spools up.

Sapphire HD4670 Review