Subtheming Omega Nodemaker or Edit Global.css

I would like to make some global.css changes.

I attempted to just add the stylesheets[all][] = sites/all/themes/concerts4charity/c4c.css in the .info file but it didn't appear to override the global.css

My purpose is to provide some custom css that will also allow me to make updates to the Nodemaker Distro without losing my CSS.

My question is; Should I try and create a Sub-Theme of a Sub-Theme or should I just edit the global.css file in the Omega_Nodemaker theme ?

If it is a Sub-Theme of a SubTheme how can I use the Omega Tools command to do so ?