Help me to choose a dual-core processor

I need a dual-core processor with heterogeneous cores (ARM + a floating point DSP). I really need a little power consumption (I expect less than 50 mW in the standby mode). I learnt about OMAP-L138, but it has 65 mW power consumption on 300 MHz that is too much on my mind.

Could anybody advise me which one should I choose?