Skimmer suggestions please?

[Picano]

I have a 20g high display tank and a 20g long sump. I want an SPS dominated tank so I know I need a good skimmer. The display tank is barebottom. I would prefer not to have to use any GFO or carbon in the system. My sump has a 13" x 11 3/4" section for a large skimmer.

I'm currently looking at these skimmers:

Octopus nwb110
Octopus nwb150
Octopus for a 125g
ASM g1
ASM mini g

I am looking to run a ulns or close to one. Help and suggestions are greatly appreciated.