Generally I say no to rear fill if someone is asking and they are interested in an SQ audio system (not video). That said though, I ran rear fill in my Avenger and found it useful. All I had were a pair of RF Power 3.5" mids on a tiny 18x2 amp and was simply connected to the rear outputs on my deck so I could fade it in or out. I found that by fading it in a little, it actually helped to raise my soundstage and focus the center a bit, but also pulled my soundstage back a tad. I dialed it in enough that it wasn't obvious it was there.

 

with rear fill

 

When doing a realistic SQ stage very very very few have successfully pulled it off with rear speakers. BIG shout out to Andy W with Harmon who is breaking new ground in this area with some revolutionary products with his multi channel efforts.

as far as enhancing the fun of a SQ system sure go for it

 

I use rears in my set up but it is heavily faded to the front.. I cant stand the sound when it is completely balanced

 

I had 4 of the same speakers in factory door locations. Then took out the rears for a week. Then put all 4 up front. Sounds 10x better using all 4 upfront. IMO .... NO to rear fill....

 

must have rear to go with the 5.1 surround kenwood dnx8120.. now if i could just find a good center channel.

rear fill is a must for me!