Upgrading my HT audio setup

[tlimof]

Hi guys I need your help, thinking of upgrading on the cheap (250 dollars) so here is my setup, I have a 3D Home Theater:
My Receiver is a Pioneer VSX 820, pictured.
My side speakers are Sony
My central speaker is a Yamaha
My surround speakers are Sony
My subwoofer is Sony

So my questions are could I replace everything with a good soundbar and subwoofer if so which one
Or just replace some of my equipment?
Or I'm set and my equipment is good for a regular size room 20x20ish

Everything works great by the way...

Thanks in advance for your help