Good luck with baby number two mate.
I am aware of those servos but 650+ dollars is quite a tall order for a servo
I would recommend hobby king:
Quick check and I found this. 25 bucks, 20kg of torque and should be more than enough.

http://www.hobbyking.com/hobbyking/s...ec_140_5g.html

I wouldnt recommend attaching an arm directly onto the servo as they just arnt designed for this kind of thing but a leaver or pushing onto a leaver mechanism would work. Its what I do on the front prongs of my robot and I havnt knackered a servo yet.