It sounds like you should definitely repot. Whenever you see new growth on a Phal and roots going off the deep end, it's a good time, provided it isn't in the dead of winter. Drench the plant before you begin in order to soften up the roots. Whether you go up a pot size will depend on what you find when you unpot. If your roots are healthy and filled the entire old pot, definitely go up a size. On the other hand, if they are less than spectacular, you may end up using the same size pot or even going down a size. Hope that helps.