Mixing DRAM is a crapshoot, even with the same exact model, there's no guarantees they will play nice. You can pull four consecutive sticks right off the assembly line and it's quite probable they won't play - that's why such a variety is offered, all sticks in an individual pack have been tested to play together - that's where the guarantee comes from, the testing. If you do try and have any problems, give me a shout