This is a common issue with proprietary home theater in a box setups. Bose being one of the most guilty manufacturers, but obviously Sony and others are guilty as well.
They are just that: Proprietary. You can't upgrade them, you can change them. You don't get the connectivity you need and you can't fix those issues.
As soon as you want to do what you want to do (as in this case), then you truly have to do a 100% replacement.
If, instead, you ask before you buy, you can often get advice in just a couple of hours as to what makes sense and what is a good deal. For well under $500 total a decent entry level setup can be put together. Even less for some of the cheaper, not quite decent complete setups.
I think Onkyo, while they lean towards weak speakers, still has the best home theater in a box setups because they use their traditional A/V receivers. So, for just a few hundred bucks you get a 5.1 setup with a real receiver.
But yes, Black Friday is almost upon us and we should see BD players available for well under $100 from major manufacturers.
Before you, or anyone else in your family balks about $100 or the money spent, consider how much it costs to go out to the movies for one night vs. how much you enjoy your setup at home.
My wife refuses to even go to movie theaters anymore, even for movies she really wants to see. It's just a far better experience at home.