Speaker suggestions

[Moviefan1203]

For awhile now, I've been wanting to upgrade our home theater but my wife has been against it. Fortunately, I cut a deal with her today. She can get a new piece of exercise equipment if I can upgrade the audio on our home theater. All we currently have is a Boston soundbar, it doesn't do a bad job but I also know there is much better out there. However, she still says no surrounds but we can get a subwoofer if it can be concealed. Why she is so against surrounds, I couldn't tell you. Unfortunately I am pretty ignorant when it comes to audio and need some advice on which direction to take. Our budget is in the $500 range. Thank you very much in advance.