+1 to what Neale said. Most any old PC less than 10 or 15 years old will work fine. I have an old PC with M3 and xylotex boad on my router and an old PC with Lcnc and a G540 on my small mill. The Lcnc combo is much snappier. Configuration not much harder or different than M3. My biggest problem was in trying to get the Lcnc to see .tap file extensions. On the Lcnc box I can be running the Lcnc and designing in Vcarve running under vine and have other things up and running. I can't do that with M3 running on windows. That machine is M3 only.
Dave