I have 3 Ddr3 hyper X 2gb ram (1600mhz). Is it possible to add 3 more ram sticks Ddr3 4gb with the other 6 gb. They all have 1

Solution
Possible, yes. Will have to try to find out, there are no guarantees when mixing DRAM from different packages - even if all were the same exact model. The forums are full of threads where people try and mix and fail