AV Pre/Processor vs 2 Channel Pre-Amp - Sound Quality

"Soix, I have a Monitor Audio 12” Silver Series Sub. I use a Sony BD 
player for movies right now, soon to be PS4 Slim, and music I have a hard drive with Apple lossless connected to my Netgear
Nighthawk router."

So, is there a DAC involved here or are you planning on using the DAC in the prepro or integrated?

What subwoofer do you have, and what are your sources for music and movies?

Unless you really care a lot about higher quality surround processing and have very good/expensive surround and center speakers, I'd use a decent AVR for processing and driving those channels.  Buying a prepro that significantly betters a decent AVR for processing along with the added amplification you'd need to buy would be a huge added expense.  But if surround music/movies are that important to you and you have the speakers that can benefit from it, it can be a perfectly justifiable purchase.