If you MUST have all four DIMM slots in play, you would be wiser to use the four Hyper X DIMMs so long as they all came together in one set. If they didn't, then it's much the same as mixing them with the Ballistix memory, as they won't have all been tested together for compatibility and it's going to be a crap shoot either way.
Please read the second section, titled "The odd man out or mixed memory" for further clarification on what is or is not possible/likely when mixing higher speed memory (Or any memory for that matter) together.
In the beginning, there was......BIOS Before you go ANY further, go to the manufacturer product page for your specific motherboard model AND revision. Revision is an important aspect because for any given motherboard there may be more than one version of that model which will be identified...
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Also, if those four Hyper X modules did NOT come together in one set, if...