I have now installed and sold several Matrix Magnum motors. They are Systema Magnum clones (but they have a polymer end bell, not aluminum) and are extremely powerful for 1/2 the price. They are the most expensive motor that I carry, but are still only $60. I also just received a large order of Element motors. They are more expensive than they used to be, but are still a super deal. Element motors are well known to be excellent Systema Energy clones. They are very well built and are known to be a "best bang for the buck" item.
Regarding the Matrix Magnum: I just installed a 500fps rig for a customer in his CA33. I used a mosfet and 11.1v Lipo to test the rig. The Classic Army motor in the gun wouln't even turn the gearbox half a cycle. I put a Matrix magnum in the gun and did no other changes. The gun works, smooth as butter. Single shot, 3 round burst, full auto all compressing an M155 spring at 500fps. Matrix Magnum motors are a "best bang for the buck" item as well.