This February, the International Poster Gallery is saying a fond farewell to Newbury Street, and hello to the up-and-coming SoWa arts district (so called for being south of Washington Street) in Boston's South End. [Gallery owner Jim] Lapides is excited. "When you are an art dealer, you constantly have to reinvent yourself...SoWa will be a continuation of that adventure [in] a new neighborhood, [with] a new, modern gallery that will have a totally different feel. Having a strong arts community around us will be invigorating. And free, convenient parking for our clients may sound prosaic, but it is a big plus."