Recent Quantum and Maxtor drives take overclocking just fine, so there is no worry regarding to that. If you're sure it's a DiamondMax Plus 40, then I would go with the Quantum, it's slightly faster. But if you can get a DiamondMax Plus 60, then get the Maxtor. The Quantum is quiet, and reasonably fast, but Maxtor DM Plus60 has faster seek times as well as better transfer rates.