The installation looks professional. I would try and find whoever did the original design and installation and hire him to do the equipment install.
You can tell on the subs based on the speaker cables. Count and match all the speaker cables to speakers. Does this installation have other zones (speakers in the bedroom, family room, patio?) After you have accounted for wires for all the speakers whatever is left is for the subs. If it is speaker wire, the subs are likely unpowered. If it is coax with rca plugs, it is likely powered subs.
Since all the other equipment was yanked, are you absolutely sure the subs are still there? The seller probably would have considered them as equipment, not furnishings.
Overall, that is an intimidating bundle of wires, and it all looks unlabeled. Hard to tell from the pictures.
Bottom line. Get help.