For something basic(ish) and not needing anything special, I'd say either a standalone controller (DDCSV), UCNC, or Centroid Acorn.

If you're wanting to do more advanced things, which by the sounds of it you're not, then you'd need to decide on what features you need in a controller, then see what controllers can provide those features.

I'll also echo Chaz, in saying I wouldn't use Mach on any new machines. I only have one machine left that still needs it, but even that I'm gradually working on software so I don't need Mach.