This work explores an enhanced magnetic spring based energy harvester design that uses a dual-mass and a geometrically nonlinear mechanical planar spring as a route to significantly improve power metrics of traditional magnetic spring based energy harvesters. Prototypes of the enhanced harvester are constructed and characterized experimentally. Nonlinear dynamical models of the harvester are developed and validated against experimental data. Additionally, prototypes of the commonly studied magnetic spring based energy harvesters are constructed, characterized, and modeled. Results show excellent agreement between model simulations and experimental data. Results show that the enhanced harvester significantly outperforms the commonly studied magnetic spring based vibration energy harvesters, especially at low acceleration levels. The enhanced harvester generates 1.97 [mW/cm3 g2] at 0.4 g [m/s2] which is approximately 400% the amount of power generated by the traditional magnetic spring based harvester, i.e. 0.5 [mW/cm3 g2]. Additionally, the half-power frequency bandwidth of the enhanced harvester is 90% wider compared to the traditional harvester. At lower acceleration, i.e. 0.1 g [m/s2], the enhanced harvester exhibits 4000% increase in power metrics compared to the traditional harvester. This makes the presented enhanced harvester design exceptionally suitable for applications where low acceleration oscillations are abundant including harvesting vibrations from highway bridges and human body motion.