In MSI Afterburner and other programs, they are displaying the memory clock before multiplying. Because the memory is GDDR5, it's bandwidth is 4 times as fast. So, a clock of 1000 actually equals 4000.
In the Sapphire TRIXX program, you edit the multiplied number. So, a value of 1200 is actually 300x4 (which is what I put in parentheses)
The more you know!
EDIT: I realized that there's an option in TRIXX to "Show effective memory clocks". If you have this disabled, you would choose 300 for your memory, otherwise you choose 1200.