You're right you shouldn't bother with a Blu-ray player.
You should get a 4K Blu-ray player, as ALIEN 1979 is getting a 4K Release soon.
But if you can't wait until then, in the meantime;
I'd recommend that you get the 2010 Alien Anthology Blu-ray boxset 6- disc that includes the two extras discs.
Then buy the prequels separately, I'd recommend the 3- disc Blu-ray set for Prometheus, 3D, Blu-ray and extras disc.
For Alien Covenant I'd recommend the 4K two disc set, as in addition to further detail the colour timing on 4K is more
genuine to the cinema release.
There's a whole host of reasons for the Anthology Blu-ray being superior to the DVD.
It simply has more extras, looks and sounds far superior for a marginal increase in price.
If you have no interest in 4K or the extras, the 6- film Blu-ray anthology is the way to go.