My current set up is denon 1913, jbl studio 190 floorstanding, 4 Polk audio monitor 45b bookshelves, klipsch synergy c-2 center. I have the opportunity to purchase 2 Polk audio monitor 70 and 2 Polk audio monitor 75t for real cheap from my friend. If i do get them. I will use the 75t for the front. and use the jbl studio and monitor 70 for rear and surround. Will it make a huge noticeable difference if I use these for the rear and surround to replace the bookshelves?