I've never liked the idea of powering some speakers off an amp and others off the headunit. I guess because I've been used to adjusting my volume with my PPI PAR245. I played around with using my HU to power rears at one time but it always seemed like it'd be well balanced at one level but out of whack when you adjusted the volume.
I use refill. I think people get the wrong impression about it or heard some not properly installed. Its like you hear them but you cant tell the sound is coming from behind you. It just enhances you front stage.