Any help about super wide angle lens would be perfect!

Hi everyone. Recently i ve decided to buy a new wide angle lens to replace my kit's 18-55.

I am not planning to spend more than 400-450 euros and i will use the new lens just for landscape photography. I have a lot of things in mind and a lot of lenses in mind again. I was planning about buying a used 16-45 lens but i think that i will need sth wider. I am considering tamron 10-24 but i have read that wide open is not sharp enough.Also Sigma 10-20 i think it has the same issues and there is no filter thread.
And lastly i am considering samyang 14mm for pentax but again no filter thread.
Do i have any other choices?
Please help!!!