I set up my media room in my house (19x13 area) when I bought it 5 years ago.

At that time I purchased ( due to ignorance ) a Harman Kardon HKTS 16 5.1 Channel Home Theater Speaker System. From that system, I have the 4 ceiling speakers and the center.

I replaced the sub woofer that came with the HITB (it stopped working) with a Infinity Sub R10

There are two standing speakers Polk RT18

The receiver is an Onkyo TX-NR676

My goal is to have theater type experience with the sound, Dolby Atmos and determine which parts of my current system should be upgraded and which parts can be left alone. My budget is from $500 to $700. I'm located in the US

Should I stick with 7.1 or 9.1 ? ( Don't know the difference ) I have seen these bipolar speakers but haven't heard about dispersion systems anywhere else and if there is a future with these.

Thanks