If the High end APU is soldered on the motherboard on a desktop type computer case it will be extremely difficult to upgrade the APU in the future. The only processors that I know of being soldered are in some old or certain laptops, depending on the type of Motherboard socket it uses.
I would think you might try and locate a motherboard with AMD Embedded graphics on it that would fit your small computer case. It would be the same as having a soldered APU in many ways.
But then again, this is just my opinion.