RE: Nvidia Quadro K5100m in Precision m6700?
For the case of you processor i7 3920xm, you can use it with the k5100m if you're cool with excessive noise (from the fan) and heat. The processor may occasionally throttle (perhaps due to excessive heat or inadequate power supply) , even with that the performance of the processor will be within range of an i7 3720qm to an i7 3820qm. So if you're cool with noise and heat, it will be fine.
NB: wattage difference between i7 (3720qm, 3740qm, 3820qm, 3840qm) and i7 (3920xm,3940xm) = 55-45 = 10 watt