Chinese based website IT168 got their hands on with RV730, the upcoming HD 4670/4650. Initial test shows that HD 4670 is really close to HD 3850 512MB，which is only $100 in newegg. The core RV730 is a 55mm chip, running at 600MHz/750MHz(4650/4670), memory @ 700MHz/1000MHz(4650/4670), shader count is 320, the same with RV670. But memory interface is only 128bit, which sounds very low end… In benchmarks 3DMark Vantage shows HD 4670 still can not easily catches up with HD 3850 512MB. But in actual games like HL2EP2 and COD4, the card performs very well, only a few FPS less than 3850. (source)

You can wade through the 20+ pages in Chinese here ... or save some time, all benchmark results in one chart: