What avr do you have particularly? If you hook a pair of speakers to the rear surround terminals then rear surround information will be played through them and if you put them in the front of the room it won't be the correct location for such. Now if your avr has that stupid bi-amp feature then you could get the left/right signal to two pairs of speakers. Having two speakers playing the same information in a channel is usually not recommended for acoustic reasons, such as comb filtering.