ACER is basically lying, but you modified the system so they absolutely will not support it or take responsibility. You should expect that.
Did you plug in the pcie power connectors? The GT 630 does not have any. The 660 needs them. What are the PSU specs? It will have a label on the side. Specifically the 12V specs. It's bound to be crappy and may not be able to power a 660. It's a very weird system setup in general