Houdini 5 will be out this year, so you can replace Fritz with that.
He is already using Stockfish 7, not the internal Fritz 15 (Rybka 4.1) engine, you haven't read his posts properly.
prfren is right, for example an i3 may have two physical cores but because of Hyperthreading report 4 cores to the operating system. You should set the engine to 2 cores in this case.
Houdini 5 will be out this year, so you can replace Fritz with that.