Strong reviews for “Xanadu” helped the Broadway tuner wrap $150,000 Wednesday.Not a huge sum, to be sure, but it was still enough to break a box office record at the Helen Hayes, the smallest of the Broadway theaters at 579 seats. A large swath of legiters were dismissive of “Xanadu,” a spoofy stage version of the 1980 movie musical flop, during the runup to its Tuesday opening. But the show, which stars Kerry Butler and Cheyenne Jackson, earned surprisingly strong Gotham press. The Wednesday night perf was sold out. Whether the reviews are enough to keep the show afloat for long remains to be seen. “Xanadu,” which began previews May 23, has not yet topped $200,000 in weekly grosses; last week, which included a handful of press performances, receipts totaled $152,820.