The native mahonias are significantly more cold tolerant....down to zone 5. And they tend to be spring into early summer bloomers rather than the winter blooming varieties you are currently growing, so spreading the wealth a bit :-)

Mahonia nervosa

Mahonia aquifolium

A type sold here as Mahonia repens* and being mass planted locally in later years has appealingly purple winter leaf color.

*2018 edition of Flora of the Pacific Northwest (University of Washington Press) notes that Berberis aquifolium, B. piperiana and B. repens blend into one another, could just as well be considered variation within B. aquifolium

I had the pleasure of seeing and smelling Mahonia fremontii growing wild one April in Utah. It was totally covered with honey-scented flowers that the pollinators loved and the scent was strong enough that I smelled it before I saw it. It’s hardy to zone 5 as well, but I don’t how flexible it is as to moisture. Where I saw it was in a canyon wih a year round stream.

https://www.highcountrygardens.com/mahonia-fremontii

Latter day botanical works are using Berberis:

"Species showing different combinations of the characteristics of the two groups are found in other parts of the world (J. W. McCain and J. F. Hennen 1982; R. V. Moran 1982), so these segregate genera do not seem to be natural. Mahonia is often recognized in horticultural works, but it is seldom recognized by botanists"

http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=103816

Since apparently even botanists are in dispute as to whether or not Berberis and Mahonia are one in the same or two distinct genera, I shall continue to to refer to the mahonias I grew up with as mahonias, than you very much!! At least the 95% of the world that are not botanists will know what I am talking about.