It seems DMM has finally realised that a 300Mhz processor is not fast enough and they are releasing a DM800HD+ with a 400Mhz processor (same as DM500HD and Dm8000). It has more connectivity than the DM500HD (notably USB) and apparently a colour OLED display, but it is seriously expensive for what it is. The faster CPU should solve the instability problems of the old DM800, especially RC problems as the box can respond must faster. Have a look at SMS for details - they are taking pre-orders.
Note: The faster CPU also has some other enhancements that will make it perform better, so it is much more than 33% faster than the old processor.