Got it, thanks!I didn't mean to imply that having a swivel is not good, I merely meant that their version of the swivel on the hose is expensive. If you are going to keep the hose that comes from Atomic as is and you don't need to use a longer hose, then it is fine, no problem. For the octo., you will need a longer hose for sure which means you will have to buy a hose in addition to the one that comes standard with the extra second stage.
The ST1 isn't sold at any dive stores here as only 2nd stage (only 1st + 2nd) and there is no ST1 octo from Atomic, so I would either have to go ST1 + M1/B2 octo or M1 + M1 octo. Buying it as an octo gives you a longer, 36" hose from Atomic.
Then the next difficult decision will be Yoke or DIN I have read countless threads here discussing that and while I prefer DIN as a connector, realistically 95% of the places I am diving at, will have Yoke cylinders, so a Yoke one will likely be the sensible choice. I've read it is possible to permanently change the 1st stage from Yoke to DIN if required at a later stage?