Recommendation for board?

I'm looking for a board for bare-metal programming. Following features 
are "must-haves":

- 2 analogue outputs with at least 16 bit resolution (real analogue 
outputs, no PWM-tricks and no audio-channels)
- one digital input and one digital output
- at least 50 MHz CPU clock (so that the application is able to switch 
the outputs fast enough)
- Ethernet and/or USB

Optionally:

- 3 analogue outputs / better resolution
- more digital outputs
- PWM/frequency outputs
- ARM CPU
- community/example codes so that the Ethernet/USB stack doesn't have to 
be developed from scratch

Any ideas which board could be used?

Thanks!