Also - if I can make one last point 
Since you will have the Aton anyway, it might be worth narrowing down, getting an idea, but ultimately delaying this decision until PFB is around 4-6 months old (at least).
Reason being 1 - you'll have a better sense of how large they are. Not at birth but the centile they settle into for both weight and height. Because if you're not likely/still undecided whether to have another child, that means you're not going to want to buy another big harness stage (Group 1, essentially) seat, as they are the most expensive and the most tricky to get right, safety wise. That means if your PFB outgrows the 0/1 seat at about 2.5, as some children do, you're going to be really pissed off and feel that you've wasted the money. You probably aren't going to be happy with putting them into a high backed booster, and so you'll end up forking out for either a forward or rear facing seat which can keep them in a harness up until 25kg, which for a child who outgrows the seat that early may be 5 or 6. Even if your child outgrows the 0/1 seat at the age of 3 or 4, you still may feel this is too young for a booster, and have the same problem.
So when your baby is born, if they are large for their age, you'll know that you will need to factor in this early outgrowing and you can decide whether to skip the rotating seat and go straight for a Swedish ERF, or whether to go for the rotating seat for now anyway but understand that the "until 4" really means "until they are wearing age 4-5 clothes". If they are about average, you would probably rule out the Dualfix, but might decide that the Vaya, Sirona or i-Spin are still worth it in terms of longevity. If they are small for their age, then you'll still have the choice of a 25kg ERF if you suddenly get hit with the urge to have the option to keep them RF until maybe seven or eight years old, or you'll have the freedom to choose between any 0/1 rotating seat, including the smaller Dualfix.
Secondly Kind + Jugend 2019 is happening in September, this is when car seat companies in Europe often announce/unveil their newest products for the coming year. That means that any seat which is currently newer to the market might have improvements added to it, but also if any company releases an even newer and better seat, their current seats might drop in price. Use PriceSpy, BTW, to check price history on car seats - with this if you have a really long window for potentially purchasing something, you can wait until it drops to a very good deal/price.
Thirdly ADAC do their twice-yearly testing and publish results in October/November, they might test the Joie i-Spin? I don't know how they choose which seats to test, so I'm not sure. But it might be worth waiting for. If you can stretch until May 2020 that will be the next test batch after that.