From what I understand you want to connect the 5.1 energy speakers to your 7.2 receiver (which one is it?).
1. And connect 2 speakers from the sony system and expand the 5.1 to 7.1.
2. And connect the sony sub to this and make 7.1 to it 7.2.
Right?
Here are the specs for the sony.
http/www.sony.co.uk/support/en/content/cnt-specs/BDV-E870/list
Note that,
1. The sony subwoofer is an passive sub. So you can forget about using it with the receiver. If you want to use it then you will need to power the subwoofer somehow.
Secondly. Even if you can connect it somehow, dont bother. That looks like a crappy sub. You are better off using the single sub from Energy. Energy classic is a pretty good budget system.
2. You could use the speakers from the sony as surround. But note that the manufacturer claims that it is 3ohm (I thought it would be an above 6ohm impedance load). If this is a really a 3ohm impedance load, then be a little cautions. You dont want to over load the receiver. If you are only gonna use it for movies then it might work out. With movies the receiver does not have to work that much.
For music stick with stereo or 5.1. If your receiver does not have thermal protection, than its not worth the risk. If it has thermal protection, and if the receiver shuts down then you know the speaker a bit too much for the receiver.