Maya animation lagging
 

Hi, I've been starting to use Maya a lot but after modeling and rigging this mech, it seems to be really laggy, especially when i try to move the model or play the animation. I already tried to use "Delete Non-Deformer History" on the whole model which helped a bit, but the FPS is still kinda low..
Don't think the problem is the PC but here is my hardware anyway:

Graphics Card: GeForce GTX 660
RAM: 8GB
CPU: Intel i5-2400 CPU @ 3.10GHz (4CPUs)

If the problem is my hardware, then upgrading which part would be most effective?
Scene is in attachements

Calculations associated with a rigged mesh and displaying textures aside, smooth preview will cause performance dips so you might want to apply this to crucial parts if any. If you want to test this, turn on the frame rate HUD in the display menu and run a quick comparison between smooth and unsmoothed.

Oh yea, after turning it to unsmoothed the FPS goes up to 24 again. But does that mean that's completely normal that it lags on smoothed mode? I could imagine that my scene isnt the most complex one either so will it start lagging again if I create something "bigger" even if I use unsmoothed and untextured mode? Or is my hardware good enough?

Thanks for the help!