A lot depends on your what your levels like now. To tell the truth, I don’t think watching with English subtitles really helps your learning much. A better idea is to rewatch a movie you’re already familiar with, with the subtitles off (or with Chinese subtitles on if you have any reading ability).
HK movies in Cantonese always have Mandarin dubs for Taiwan releases btw, so don’t rule them out.
There’s loads of good Taiwanese and Chinese movies to choose from. Check out this thread for some ideas:
Personally I love watching Taiwanese films. Edward Yang and Hou Xiaoxian being two of my favourites. Sometimes they might have quite a bit of Hokkien/Taiwanese language too though. But these movies often have a lot more everyday Chinese in them than kung-fu epics and HK gangster movies. There’s a Taiwanese film called Cape No. 7 on at the cinemas which is proving highly popular. I think it’s already the highest grossing domestic film ever, by a long shot. A real boon to local film-making. I have yet to check it out.