Best toy for achieving a super-O ?

I've been using the helix syn for over a year now but still not gotten the experience of a super-o.

Progress for a significant number of men can be very slow for a number of reasons, please see Identifying Obstacles to Progress for some guidance here. Most of these obstacles are of a psychological nature rather than a physical deficiency on the part of the person or the device being used. Overcoming and/or resolving those obstacles should be your first approach for a solution rather than just getting another device.

Was wondering if there are better or bigger massagers that will give better results in this pursuit ?

There are hundreds of prostate massagers in the market place, some bigger and some smaller than your Helix SYN. All of them will induce slightly different sensations in use depending on the individual's sensitivity and attentive focus.

First off bigger is NOT inherently better for generating pleasurable performance, small massagers can be impressive performers, it is more a matter of each man's unique physiology/psychology which determines better results, not the particular model. You might get a little insight from reading the related thread The Best Aneros model is....

Second, there is really no consensus of definitive criteria for determining 'better' or 'worse' performance from any particular massager, it is largely a matter of individual subjective opinion, kind of like asking someone if chocolate is better than vanilla. One massager may work optimally for one man and yet be ineffective for another. Most members here do have their favorite models, but even those are subject to variation depending on a users mood at the time of use and his desired sensual experience.

The best advice I can offer you is to follow your intuition when deciding to try a different model but remember the device itself is probably less than 10% of the sensual experience, 90% is in your mental processes. Please see @rook 's thread Whole Body/Whole Mind - the mental side & @SteelColdiron 's thread Aneros: The Essential Mind State for a little insight. It might also help you to read @neros 's post The truth behind how to "rewire".

IMHO, the Helix SYN is a good, versatile model, it has been very effective for a large number of men so the odds are good it will still work for you if you have eliminated all other obstacles. You might find the thread Identifying Facilitators to Progress helpful in establishing a beneficial environment for your future Anerosessions.
Good Vibes to You !