nPlayer and Infuse are great options. Depending on your wishlist either one is great and supports AC3.
See this and this topic which indicate quite a few good ones. I prefer nPlayer (app / site) and Infuse (app / site). They aren't cheap but do offer many features.
Before you buy Infuse double check how much it ends up costing over time. I don't own it and haven't followed in depth but I have seen other people complaining how often they charge for updates.