What type of electric drive would you suggest for this?

[bikemad]

for my next bike project i am trying to find a rebike frame and fit it with an electric drive system. my budget is 500 dollars and i have a feeling i am going to be building the frame and other components and saving a bulk of the money for the electric drive. now i dont have much experience with electric kits.
so i was wondering if anyone out there had some helpful suggestions on what type of drive i should use. to give you an idea of the frame setup im working with here is a picture. any help is very useful, ill be starting from the ground up on this one
http://www.intrepidequipment.com/recumbent

thanks guys
steve
http://www.intrepidequipment.com intrepid handcycle specialist

[ghost]

Sell it to San Quentin to replace " old sparky " LOL.