Thanks @Percymon! I just happened to read about LiPo batteries today as well and I agree that 2 cells lipo is probably the best. I have also decided not to upgrade the motor and electronics for now, until one day I really know what I am doing regarding the electronics.
Just to share:
https://www.msuk-forum.co.uk/forums/topic/21028-lipo-the-big-guide-thread-updated-march-10/
Also, @unixphreak are all P407 ungreased and unoiled?