Blunt, but I'll take it.
Is TriXX capable of doing this, or is MSI AfterBurner the way to go? Also, is there a way to have AfterBurner clock the memory down to 300 MHz?
Trixx is the way to go if you're over clocking sapphire cards. Run afterburner to monitor the temps, clocks, fan speeds, etc. Uncheck synchronize cards in Trixx's settings and set each card upon rebooting. Trixx can monitor the cards but not quite as nicely as afterburner can.