Which 7.1 Receiver Should I Buy I Have Pioneer VSX-D812 7.1 Channels Receiver And Need Advise On What Speakers To Buy?

I have Pioneer VSX-D812 7.1 Channels Receiver and need advise on what speakers to buy? - which 7.1 receiver should i buy

I love this receiver, but I have an old Sherwin Vega, left, right speakers and the Sony Center, Surround left and right. I Like to upgrade my speakers to give me better sound speakers with a maximum of $ 700. Can anyone help me with this?