Usually the dectron 5w60 is the widest range that will have to be programmed.
This procedure will take more than a few minutes of coding.
Wireless frequences resolutions.
I don't know about all that but I have some Ultrazone Pro 650's and their impedance @ 1khz is 80 ohms and they work pretty good for me. Hope that helps some.
I don't think the ohms matter much specifically. I've used all sorts when I had an Axe Fx II ... there's no "proper" one, just ones that sound good to you. My Senn HD280s are good for me.