I wouldn't even bother with the Energy center, just get the surrounds and go without a center. What exactly IS the budget then? Your room is pretty decent size so you aren't going to get away with a bottom basement sub. The STF-2 will likely give you plenty of output even in that room, but it is not going to extend super deep and give you that silly grin with movies. While it will definitely sound better than the JBL, it probably won't go much lower than the current one.