I don't know what your budget is. Dakota actions have a very good rep and I know a couple guys with them that love them. I personally wanted a Sako action on my custom, but they no longer sell just actions and I wasn't willing to pay the price of a new Sako just to pull the action. Being left handed, and set on stainless and an action long enough for the 7mm STW I settled for buying a used Browning with only 9 rounds through it for about 2/3 the price of a new one. I had it worked over by a good local gunsmith (the only one I've ever used I would recommend for anything more complicated than I can do myself) and have been very happy with it. I know Browning actions aren't common for custom builds, but it is smooth as silk and will shoot well under 1/2 MOA out at 800 (3 inch groups). Obviously the barrel and other components affect accuracy also. But for my budget I had it built on the factory stock with a Hart barrel for well under $2000. It would shoot great off of sandbags like that, but the factory stock was too flexy and when I put a bipod on it if I leaned into the rifle it would bow the stock up and touch the barrel. I missed a nice whitetail 3 times at 450 because of this, so bad it didn't even scare the rutted up buck and I was able to move and figure out what the problem was and drop him! After that I put a Macmillan on it and have been very happy.
You can spend a lot of money on a custom action or you can find a factory action you like and will fit your requirements and then pay a quality gunsmith to work it over. If you're on a budget price them both before you decide.
I don't know a lot about Wyatt boxes, but a quality gunsmith should be able to tell you if they will work with any action you choose.
