Cannot fit more RAM because of current CPU Heatsink.

PhysX_HW

Distinguished
Don't buy the 8Gb module. It is likely that you would run into compatibility issues with that configuration, as you should use the same number of dims on each channel, because Intel CPUs are very picky about this.

It might work though, so if you can try it before you buy it, then go for it. But I can't guarantee that it will.