Best CPU (performance/consumption ratio)?

[jfr2006]

Hi:

 

   First of all, sorry if this is not the right sub forum for this topic, but i tried the search without any results. I'm currently the owner of a DS716+II with a DX513 expansion unit, I'm planning on replace the DS716+II with something more powerful and probably try to keep the DX513, if possible. 

 

However i would like to not increase the power consumption to much, since this is a system that is turned on 24/7. So a little help here: what could be the best CPU in terms of power consumption and performance ratio? Something that is adequate to this, but with a TDP for example of 35W? 

 

Thanks and regards.