I agree:Speakers
I'd start with upgrading the speakers, then, as finances permit, buy amplifier(s). Those Balcony's are fine for the sides and rears, but you'll surely benefit from upgrading the L, C and R's. You'll notice the difference from that, but you'll soon want more power to get that movie theater experience.
For movie theater sound especially, I'd recommend looking at pro-amps in addition to home-audio amplifiers. Some other members on here have similiar feelings on the matter. Home audio products have bigger margins. Go to bhphotovideo.com and surf around the pro-audio amplifier section.