changing stepper motor sd3

HI

I'm gonna have to change the carriage as I brocke one.

so while doing this, I was wondering if it was a good move to replace the original stepper, they heat a lot,

and I read somewhere on this forum that they where push over the limit.

(like more voltage that they should)(on stock sd3)

now what sort of stepper would be an upgrade?

I don't even now the exact model the sd3 use. (they look like nema 14) 

I have another 3d printer a microdelta and it use nema17 they are bigger for sure.
and they never heat even  when I print for 18+ hours.

The solidoodle cannot print 8h+ without some sort of heat dissipation

I know by the look of it the only thing that will still be stock will be the frame.... 

but it's a very good one...