I hate to say it, but you are kind of screwed on space limitations. I wouldn't bother with loudspeaker upgrades until you have somewhere to put them. That chair on the right and the equipment stand on the left are killing any potential you have for better sound. Can you move the turntable and receiver onto the center cabinet there? And maybe move the games, records, and controllers into the cabinet? If you can do that, and find another place for that chair, you might have potential for a great sound system. If you can do that, I would get a pair of Polk R700 speakers. I would also scrap the center speaker there, because it would be a liability when used with the R700s. Same with the sub- don't try to run that sub with the R700s, it would do more harm than good. I would also even considering just taking out the surround speakers at that point, so the amplifier power is totally reserved for the R700 speakers. Maybe put them back up when you get a better receiver.