Shipping 27" iMac within US

Shipping 27" iMac within US

We're moving (and before anyone asks, cross-ocean, so just taking it with me is not an option) and I would like to move my (2016) 27" iMac. While it would be easier to just try to sell it locally, where I'm at, it probably wouldn't even sell for a hundred bucks. There's no demand. And while I wouldn't have the hassle of trying to get it where I'm going, it would also mean I'm out of a working iMac (when a new one would cost an arm and a leg and doesn't exist in 27" any longer). So I'm willing to go through the exercise to take it with me, somehow.

Taking on the plane as checked baggage is not an option. I already did google, airlines won't allow it.

Has anyone recently shipped an iMac within the US and can share their experience? I've found a few threads, but they're older.

I have the original trapazoid box with the styrofoam, but because I picked it up at an Apple store back when I bought it, I do not have any other fitting box to go with it. I know you can buy them online, but those boxes alone are somewhat like $70...

Also, what is the experience of people using Fedex over UPS? What shipping costs could I expect?

Thank you!