There are many very attractively priced evaluation boards available form various vendor and suppliers.
I don't think a specific answer can be given to such a generic question.
This is the same question you asked: "If I buy a random board from a random vendor can I makes changes to it to increase its memory?"
The only proper answer is: "it depends..." Depends on the board, the architecture of the processor, the actual processor on the board, etc.
Ask about specific boards / processors if you want a real answer.