REGENT SEVEN SEAS CRUISES completed a multimillion dollar upgrade of its entertainment programming, and now has professional ballroom dance teams, new productions and what Regent says is the largest live orchestra on any luxury cruise line. Shows like ABC's "Dancing with the Stars" contributed to Regent's decision to add several shows with professional ballroom dancing and to offer complimentary lessons to Regent guests. Its nine-piece orchestra will perform as a unit on the Mariner, Voyager and Navigator, and will also break up into smaller units to perform at cocktails hours or in lounges.