RE: ... 'have at it with your pontifications'
There is nothing pontificating here. If you have USD 12000 - you buy neat finished product. If you have USD 2500 - 3000 and OEM acquaintances - you may buy and have within a month the very same computer system ... and a lot of personally acquired know-how. The know-how itself is the greatest reward of all that.

If you take the risks and win - you win 9000, and if you loose - you loose your own time (by the hour rate there) and maybe about USD 500 - 1000 for inappropriate and incompatible or impeding the speed hardware.

The choice is personal. No advises could be given on that.
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A Tip: Assemble a computer platform that has been already assembled somewhere and sold commercially, and proven to work well on linux.