Keep in mind though that on the overview page it says: "The specifications may differ from areas and we keep the right to change without notice. Please check the specific Specification with your local dealers." So you should ask for detailed specifications from your dealer.
A possible problem in budget pre-built PCs is the powersupply. Can it really handle what it says on the lable? For example I have two old powersupplys that are both rated at 300w. The other weighs ~1kg and the other one ~1.8kg. I assume the heavier one has more capable circuitry .
Then another problem is the motherboard powercircuitry and what it can handle. The specs for retail boards and OEM boards for budget PCs may not be identical you should contact your vendor and ask if athlon 860k and radeon rx460 are supported. And if possible buy them from the same place so it is their responsibility to sell you supported parts. Atleast that's the upgrade I would choose.