It depends on how you run them - if they're always going to be going one direction, like on a continous-loop mainline, I'd put the powered one first. If you use them on a point-to-point commuter line, so they'll be going forward and backward a lot, I'd put the powered on in the middle...but be aware that not having the powered one up front could cause some derailments of the non-powered units unless they're properly weighted.
FWIW all Budd RDC cars were powered, they couldn't pull even one extra car by themselves.
