[BrianG]

FWIW, the temps on the Quark ESC may be misleading. If the internal thermal pad (that holds the FETs to the case) weakens, let's go, or is making poor connection, the heatsink will seem cool, but the FETs are actually really hot. Take the temps at the motor wire output. If they are really high, you might have to do the "internal mod" to the Quark to help cool it. This involves taking the ESC apart, removing the thermal pads, fabbing a new spacer/heatspreader, and thermal epoxying the spacer to the FETs and the case. This voids the warranty, but makes for a much cooler running ESC since the heat is being drawn away from the FETs much better.