I found the sweet spot but it's 5ft off the floor

I do not understand your problem. When I sit in my seat my ears are between 4' & 5' from the floor. The sweet spot is never at floor level because the speaker drivers are not horizontal along to the floor but vertical from floor to ceiling except center speakers for HT.

Is your head above the chairs back, also do you use a chair or couch? If you sit forward does the sound also get better? Where is the sound stage, high on the wall or at head level and lower?