Certainly check the connection. Also run the auto-calibration routine if there is one.
Nightlord is right that center speakers like that are always sub-optimal, but they can work fine for certain seating locations. I don't think that's really your problem at this point. Still, when moving forward to a final set of equipment, his advice is right.
The issues you are having are probably best described by the Alison effect, or SBIR. It's a slightly complicated acoustic problem caused by reflections from surfaces near a speaker. Once you get some drywall on the ceiling, everything will change.