Its up to you.
If its just going to be used as a display machine you can get something cheaper in the PC line.
It might be better speaking to a custom build merchant with what you want to do.
Again depends if you using it for other things and you want it to be mobile.
That's a colour calibrator.
Its a pain in the bum having your work machine as the display machine. Better to have a display machine of what ever flavour you like so it can sit and do its thing. Then have another machine which does the processing.
As said the display machine just needs high graphics and a SSD for data transfer and a decent cooling system but nothing special. You should be able to pick one of them up of 500$ for the base unit and another 500 for the graphics cards. Your better to have a card per output device.