Any of the models can achieve super-O?

I believe that's basically true, arguably some are harder to master though. Also I've found that certain models work better at different times, and different models to have different 'personalities', so I'd still recommend the whole productline. I understand if you are yet to achieve a Super O you might be a little apprehensive buying the whole range, but really try it with a little mj and you will look back on your decision to buy an Aneros as one of the best purchases you ever made!

Helix is probably the best beginner model. If I was to get just one model, that would be it.

Helix is probably the best beginner model. If I was to get just one model, that would be it.

Agree with The_Bishop. Starting out, avoid the extremes in size and as in bowling aim for the center of the lane. That's MGX or Helix. While MGX might be easier to master, the Helix offers some quirks that will provide some interesting sensations later in your journey. Compare to buying a single speed bike or one with a dérailleur.

The other tools are like buying more specialized machines..