The expression "sitting well with" means to feel comfortable or agreeable with something or someone. There are several synonyms that could replace this phrase, such as "fitting well with," "matching well with," "meshing well with," or "jibing well with." Other options could include "coexisting well with," "complementing well with," or "harmonizing well with." These phrases imply that there is a sense of compatibility, alignment, or congruence between two or more things, people, or ideas. Ultimately, the choice of synonym will depend on the context in which it is used and the specific nuances that the speaker wants to convey.