From the manufacturer's website
FAQ page, aesthetic placement is just fine. There are "better" places to put the panels (i.e. first reflection points), but they indicate that you can put them anywhere.
I would think that one area would be the side walls in terms of first reflection points. I also believe that you are of the correct thinking that you'll benefit from putting panel directly behind you if you are sitting close to a back wall. In addition to any assistance from folks here, I'll bet that you could get some great help from the manufacturer.