The T-Bred B core is the one to get the XP1700 DUT3C is a core that graded out needing 1.6volts to run stable where as the XP1700 DLT3C only needs 1.5volts to be stable. The DLT3C overclocks better because it runs stable @higher MHZ with voltage increases, because the DUT3C needs more voltage it hits a wall sooner that the DLT3C does.

Unless you base your life on benchmark scores then 2000mhz+ is plenty fast enough the XP1700's are being reported as doing 2100-2400mhz on air ! at $40+ a chip thats hard to beat !