I;ve decided that I want to add a rotary axis to my shapeoko (as well as add the ability to do surface mapping), so I need to change my controller out.  No big deal other than I have no clue what I need to put together for the kit.  I have the windows computer covered.  I am thinking of a Smoothstepper ESS and a HobbyCNC board to drive the motors.  Am I on the right path here to get to a point where I can use Mach4 with this machine....

Hi,
 I use mach4 and an ESS and have done for seven years, and the combination will drive your four axis machine no trouble.

Mach4 has a surface mapping module called mcSurface. Its really meant to probe the nominally flat bed of your machine for small deviations from 'flat' and then to process
that data such that the machine automatically compensates for the bed not being perfectly flat. This may not be what you had in mind.

I use a software (freeware) utility called Autoleveller that was intended to probe PCB blanks and compensate (via Gdcode edit) for a not perfectly flat PCB blank.
This software can be used in creative ways and may be adapted to your requirement. The software is open source so you could modify it or rewrite it at will.

There is another freeware software solution, the name of which escapes me at the moment, that uses similar ideas to Autoleveller that may be even better suited to
adaption to a particular purpose.

Craig

I;ve decided that I want to add a rotary axis to my shapeoko (as well as add the ability to do surface mapping), so I need to change my controller out.  No big deal other than I have no clue what I need to put together for the kit.  I have the windows computer covered.  I am thinking of a Smoothstepper ESS and a HobbyCNC board to drive the motors.  Am I on the right path here to get to a point where I can use Mach4 with this machine....

You are on the right path. I have Mach4 running my Shapeoko.  I am using the ESS with a C25 breakout board and Gecko G203V for the motor drivers. works like a champ.