In planning you need to start farther back
Plan the general use of the machine
Plan the software loadout
Plan the OS
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If this machine is a simple home machine for me, I will want to do some cad and general office stuff (I'm boring...). I will be using BRLCAD and Libre Office as well as the requisite time waster games, so I will be running Linux. The hardware loadout then becomes clear.
In the office I will need some additional capabilities, most notably to use a vendor's AutoCAD and Visio templates to save a ton of reinventing the wheel, but I will also be running on a Linux platform, so virtualization is important, sufficiently quick to run AutoCAD to strip the data from the customer's design and Visio. Under Linux we will be running a 3D modeller, and general office gear on two 1080p monitors. Again, the specification of the purpose, software, and target OS make the hardware pretty obvious.