Avi, welcome. Sure, in particular the QS8s would add a lot of enjoyment with surround for both music and movies. Generally, new mains would make the greatest single improvement, and M60s would be suggested if you might consider replacing the Pioneers.
As for a new receiver, there're several excellent ones in that price range, certainly including the Yamaha 1800 which was mentioned if it can be found at that price, but let me draw your attention specifically to the special now at
Vanns on the Onkyo 705 for about $650 with free shipping.
Also, forget about buying the Monster speaker wire. There's no good reason to pay that much and probably you should simply go to a local source such as Home Depot or Lowes and have them cut you what you need.
