bcarithers: It may be partly due to the Pioneer sub providing the boominess and/or combination of it being in the top right corner. Try moving it 3-4 feet down on the right. Another location I would try is on the right side in-between your recliners and the couch on the bottom. Gives you a bit of nearfield for both seating arrangements.
slow ride: There are no hardset rules on sub placement, one generally has to try different locations if possible. One being near the front left or right speakers (generally the easiest due to available space), near corners (not necessarily in a corner but hug one wall while moving away a few feet from the other), nearfield (being close to your seating position is another method). Everyone's room is different so it is hard to say "put it here", etc.
A SPL meter is a very handy piece of equipment to have for setting up speakers and subs. They are inexpensive and can tell you far more than just using your ears.
There are a ton of links, do a search here or over at Google for terms like subwoofer placment, crawling for bass, nearfield, etc.
