How does it interface with the machinery? As far as I know cam means the cnc machine wired directly to the computer.
For cad work it boils down to if you can get a quadro, do so. Otherwise it's raw cpu power which wins it. For £1300 you're going to struggle with getting a professional graphics card, but even the cheapest quadro you can find will be much better than a gaming card.
Most cad software costs more than the stated budget, so unless it's being donated by work/university I'm not sure how well this is going to work out. What software will he be using?