Yes, and yes. You can lightly trim your Spiraeas when you move them as these tough shrubs handle winter weather well. Adding good potting soil to the current soil is fine but most shrubs prefer added compost or fine bark as potting soil does not hold moisture around landscape plants a well as compost. Bagged compost is also less expensive than potting soil. A mulch on top of the soil is your best insurance after a transplant and the easiest way to pamper your landscape shrubs. Keep growing, Marianne Binetti