If all goes well, I should start my rebreather training within a month. I am very much looking forward to it, with all its challenges & interesting points. I can see the skills I will learn as a way to open up new possiblities & opportunities for me. I will be training through my LDS which offers the both the Posiedon MK6 & the Hollis Prism2. After studying & comparing the pros & cons of each unit, I have decided on & ordered the Prism2. The Prism2 offers more of what I am wanting to use the unit for now & possibly in the future,... primarily cave diving, but perhaps some Trimix, as I grow, in the future. I am also more familiar with the Shearwater computer on the Hollis, as I have 2 Predators that I dive OC with. While there is not much really wrong with the Posiedon, the Hollis just seems better suited to my needs. a decision of matching the right tool for the eventual dive objective.