wait a sec for gtx 1080ti...with my setup i'm exceeding regurlaly 400w of total power used (oc r7 1700x and gtx 1080ti oc)..I would say if your Dell 330 is "crapping out" with the Zotac 1080 and 7700K then you need to get another Dell 330, because yours is not good. That brick in my experience can power that combo constantly with anything you can throw at it. What will be interesting to see is how the two bricks compete when moving to the 1080ti or overclocking (though overclocking in a MINI is stupid. Buy an Ncase or something.)
Coil whine with the HDPLEX 300 AC/DC and HDPLEX 400 is almost non-existent. It is the best 19v-24v DC solution I have seen and on par with many 12v solutions. This doesn't mean your GPU will not whine (but it might help...trying to get some more 1080s to test simultaneously).
Alone my msi gtx 1080ti gaming x can reach 330w..
Anyway, it's a very good progress from hdplex about coil whine..