ᐅ Gas condensing boiler – the challenge of choice

Hello everyone,
Our planned house construction is getting closer.

At the moment, we have been dealing with plumbing and heating systems. Since I am a complete beginner in this area, I actually have more questions than answers.

We have received 3 quotes from different heating and plumbing companies. All three offers are in a similar price range.

Now to my main problem:

- Company A offers a Buderus GB172-14 with a solar package
- Company B offers a SolvisMax also with solar
- Company C offers a Vaillant Ecotec Plus VC 146/5-5 E

We have set the requirement for a KfW 55 standard, a ventilation system with heat recovery, solar thermal system, and underfloor heating throughout the entire house.

Can you tell me something about these manufacturers and which type I should choose based on the models?
For example, I have never heard of Solvis before. Buderus is well known, and so is Vaillant.
In our area, there is another company that also distributes Solvis (including customer service).

Thank you and have a nice Sunday
Sönke