Amplifier for rear channels

Who made your front and center receiver /amp? For sound continuity you may be able to get a 2 channel power amp by the same manufacturer. Which speakers are you using?

Unless you rear speakers are more than cubes I wouldn't bother with upgrading the amplification for them.

I have "junk" rear channels in my 4.1 system and I have never noticed them lacking for movies. Even when listening to surround SACDs I don't notice a deficiency unless the recording is centered in the music. I have a LAGQ SACD that places each guitar in a different speaker and it obviously doesn't work with my Focals opposite the "junk" rears.

I would consider putting the money toward something else.

If you're talking about going 7.1 then there may be some gains, but I'm a big fan of 4.1 or 5.1 over 7.1 unless you have a dedicated room for movies. I just don't think it makes that much difference to the movie experience where visuals distract quite well.

I am using RF-7, RC-7 DeanG and RS-7. Ampilier is a BAT-VK-6200