The Polk Speakers are a Great choice due to their price to performance ratio.
Looking over your room I see space can be somewhat tight.The larger,seperate Polk speakers need more space to perform at their best.
The new Receiver is a "Must Have".It will allow you to decode the surround sound from your Blu Ray Movies and transmit the correct signals to the correct speakers(surrounds,center,fronts,sub).
Also with a receiver you can get one that will allow you to connect 3 or more HDMI Cables to the receiver.Then you have one HDMI cable leading from the receiver to your HDTV.This will allow you to connect your PS3 and other future additions.
I would look at some of the small Home Theater Speaker Sets.Since you are across the pond,in Australia ,the great prices from NewEgg may not apply to you.If they dont then the speaker sets are even more of a good choice.
The Polk RM Series Sets and a Klipsch HD Set are all outstanding performers.They are smaller in size but produce Big sound with an outstanding Surroundfield performance.
The speakers have optional adjustable speaker stands for use with them(and to get the speakers at the exact height needed for the best sound)Then they also include brackets to wall mount the speakers to help conserve space(and for the surrounds,place them in some great positions).
These links are from NewEgg but,the prices may vary for you in Australia.
Polk RM-6750:
http://www.newegg.com/Product/Produc...82E16882290066
Polk RM-705
http://www.newegg.com/Product/Produc...82E16882290113
Klipsch HD300:
http://www.newegg.com/Product/Produc...82E16882780017
You have already received and will receive much more Wise advise from the Many Outstanding Members here at the Forum.
So,I believe you will end up with a Great System for your use.