As said a few times.
Definitely keep the 3500, until you KNOW why it won’t suit your situation, and what you want different, like power, or features.
Speakers look good, but the sub has gotta go... Good news is that the room is small so you won’t need some behemoth, but you’re definitely missing a lot of bass. Qualitatively AND quantitatively. For movies especially, as
@Pogre mentioned the one you have does not play very deep/low. I know that’s a tough concept to grasp, especially when you probably do have bass throughout the space.
What you probably don’t realize as well, is that your little sub won’t be as linear and controlled as a quality sub.
Have a little faith, and you’ll see what we mean!