I know you want to build it yourself, and having done so many times myself, I admire you for it.
However I would suggest you go to somewhere like Novatech, and see what they have to offer ready built, or how much it would cost to build one to your spec.
The reason I say this is, it is now just as cheap to purchase a high spec machine or even cheaper than to build it.
Coupled with this, most come with a very good warranty which if you build yourself, and you do something wrong, your attempt is somewhat thwarted.
Novatech, go to
what ever way you choose, I wish you all the very best.