Airspy HF+ (Coming soon) can run on a 1GHz Pentium computer or Raspberry PI 3.
The specs on this Airspy HF+ says this is a DX beast Tuner. http://airspy.com/airspy-hf-plus/
Author of Airspy & SDR# Twitter page here at this link. https://twitter.com/lambdaprog/media scroll down his page to see testing of the Airspy HF+ & few other things he is working on.