The D1000 is possible but slower. Adding three dice together is OK so long as they are 3D6 or similar small numbers. Adding more than 3 small dice together should be avoided. People are used to adding dice and reading percentiles. They are generally not used to, say, cancelling out doubles.
Testing is the best way to be sure.
All this gets you to a basic die result number. This can be a significant step. The time spent on these add up so the more you have, the longer it takes. With respect to math, addition is the fastest. Subtraction and small multiplications are the next best.