@AlwaysStranger :
In English, there is no perfect translation, but the words used in Arabic (wa-ma) include living beings and non living beings altogether, instead of another word wa-min which refers to only non-living things. So these two verses are already pointing out that there is other life as well created in these six stages. Here are couple of other verses which further elaborates that there is indeed life in the universe.
[30:27] And to Him belongs whosoever is in the heavens and the earth. All are obedient to Him.
[37:6] Lord of the heavens and the earth and all that is between them and the Lord of the sun’s risings.
[42:30] And among His Signs is the creation of the heavens and the earth, and of whatever living creatures He has spread forth in both. And He has the power to gather them together when He pleases.
Note that Sun’s risings - the word used is plural of East. In our context it might be referring to other places in the universe where sun rises on some intelligent beings. Sun rising also means these planets are rotating on their axis like Earth.
Now coming back to the original question of six stages, Personally, I believe that these verses refer not only to six stages of creation of the universe itself, but also it is dividing the creation of our particular solar system, and later life on our planet Earth also into six stages. The reason for this is some other verses which give more details of these six stages like following:
[41:10] Say: ‘Do you really disbelieve in Him Who created the earth in two days? And do you set up equals to Him?’ That is the Lord of the worlds.
[41:11] He placed therein firm mountains rising above its surface, and blessed it with abundance,and provided therein its foods in proper measure in four days — alike for all seekers.
[41:12] Then He turned to the heaven while it was something like smoke, and said to it and to the earth: ‘Come ye both of you, willingly or unwillingly.’ They said, ‘We come willingly.’
[41:13] So He completed them into seven heavens in two days, and He revealed to each heaven its function. And We adorned the lowest heaven with lamps for light and for protection. That is the decree of the Mighty, the All-Knowing.
To me this also shows the significance of the number 6, plus a 7th and the final when creation is completed and has start performing its assigned functions or duties. This 7th stage is what the Quran refers to as He settled Himself on the Throne. You sit on a throne, or on the chair of authority and control, when your creation is ready to serve its purpose. Its a metaphorical reference.