Yes it's basically the same as 957DW+. It's not a new model, available for at least 5 years.
Do you have any further information about the quality/longevity of the 706W?
Quick makes reliable equipment, I don't think you will need to replace any parts ever.
What appropriate alternatives under 150€ would you recommend for a beginner?
If you want combined station, I don't think there are better alternatives at this price.
Any idea why it is not listed on the official Quick website?
Many models are not listed, also it depends on which regional website you are visiting.