Why not just use a 5.1 or 7.1 wallplate that mounts to a 2 gang device box? Then add a blank plate with keystones you can configure however you like. They use them for data jacks but you can get coaxial and speaker keystones just as well at HD or lowes.
For more room you can use a deep 4x4 with a 2 gang plaster ring. Done it lots before and works great.
As for bananas vs bare wire affecting audio, I have used bananas ever since I got "serious" about audio and they are an added cost for sure. If you get the kind with a locking tip and a set screw on the wire connector, and use anti-ox on the wire to connector joint, you will have a zero maintenence, trouble free connection until the archaeologists exhume your system 1000 years from now.
Bananas make terminations on the back of crowded AVRs a breeze! Totally recommend. As for SQ affected: totally bogus.
I use the sewell brand plugs. They are clones of the high end ones and are an awesome value.
