Hello :)
You have quite a few options for the next stage after the infant carrier.
First of all I'd advise that it's very important to keep little ones rear facing. Certainly for the next few months, but ideally for the next few years. It's safer for everyone to rear face at every age, but it's most dangerous for children around 1 year old or younger to forward face.
So you could go for the Sirona Z - this is a nice seat, fits on the base you have, can rear face up to 105cm / 18kg (this is about 3.5 years - maybe less if your little one is tall) and can also forward face later if you would like to, still only up to 105cm/18kg. It also spins which is a handy feature.
Or you could go for a different isofix spin seat which goes on its own base, usually the bases are built in so you wouldn't need to buy one - this would free up the base again for your infant seat in case you have another baby. There are lots on the market - Britax Dualfix, Nuna Rebl Plus, Joie 360 Spin etc. They're all a similar size so rear / forward facing until 105cm or 18kg.
One issue with the seats up to 18kg/105cm is that taller/bigger children can outgrow them early which means you then need to look for a bigger seat up to 25kg / 125cm. This might not be an urgent issue if you think you'll have another baby and want to pass the 18kg seat down to them anyway. But if you want to be sure that it will last, you might want to go for the bigger seat straight away.
So if you want to rear face for longer, there are seats which accommodate up to 25kg rear facing, which is about 6 years. They're a bit more roomy than the spin seats and tend to have better leg room for the child. These would be seats such as Axkid Move / Minikid, Britax Max Way Plus. They don't go forward facing at all, but they will definitely take you right up to booster seat age so you don't need to buy a bigger seat later.
You can get seats which convert into a booster seat for later and so claim to last until 12 years, I personally think they're a bit of a false economy and tend not to make the safest booster seats - you're better off concentrating on this stage and then getting a separate high backed booster later.
If you're not sold on RF to 25kg, but want to be sure to harness to 25kg, there are a couple of options - BabyAuto Dupla, or Maxi Cosi Beryl. BabyAuto can rear face to 18kg, Maxi Cosi only to 13kg.
If you are sure you want to forward face after this seat, I'd recommend either one of the spin seats as mentioned before, or a forward facing only seat up to 18kg/105cm, not one that converts to a booster - these are a bit more cocooned and protective for a younger toddler. However if you are going to do this I'd recommend to stay in the baby seat at the bare minimum until 15 months, or ideally until it's completely outgrown as you can then squeeze those last few months out rear facing which will make a huge difference.
You can buy seats for this stage which have an impact shield instead of a 5 point harness, but I wouldn't recommend them - the harness seems to protect children better in real life crashes.
Sorry that's a lot of things to look at/consider and probably hasn't made things any easier! But maybe it helps to know about the different categories to narrow things down.