I have the Helix and Progasm also like Kurono.
The Helix performs better for me, even though it's smaller - however everyone is different.
If it were me, start with the Helix.
The point of the Aneros is movement and massaging the area. If it's too big, it may not have fluid movement and that defeats the purpose.
You have to completely relax when using it. Dedicate time to it. It's not a Pop it in and suddenly this lightning explosion orgasm. Doesn't work that way.
If you completely relax, and spend 15-20 minutes warming up, you'll notice your body starts to take over a bit. Focus on breathing too.
Suddenly your body starts to tremble and the pre-cum starts to flow.
Keep going. The longer you spend, the more intense the internal orgasms get, which will lead to an external.
If you just want to pop a nut, save the coin, get a cheapy prostate poker.