You should try the Sony's analog outputs to see what they sound like. Use the Bypass, or Direct, feature on your receiver if it has one, it will allow the analog signal to bypass all the HT circuitry.

There have been some good ideas on improving your presentation but the fact remains if you don't start with a good source up front (CD/turntable etc. ) you just won't get good sound no matter what. The rest of the system just passes it through, it won't build it up or improve it. Start with the source and maintain the signal the best you can until it exits your speakers. Then hope your room is friendly to it. It don't make sense to do anything with speakers, or amp, if your source isn't as good as your budget allows. I don't know which Sony you have, it may have potential but your Pioneer is a definite weak link. #1, it's a jukebox, and #2, it's very old DAC technology. You chose the right part of the system to upgrade first. It's your sources job to extract the detail/information off the software (CD), once it leaves your player, nothing down stream can add to it. Other components will have different presentations or delivery of the signal but NONE will add detail or information that isn't there to start with. If your have a poor signal coming from the source, switching speakers won't do anything except let you hear that same poor signal in a new way. If a recording allows you to hear the breath of a sax player but that information doesn't come out of your source, it's LOST, and nothing you will ever do down stream in the system will allow you to hear it. I don't see how this can be such a difficult concept for professed audiophiles to grasp. The point is not to change the sound, it's to improve the sound. If "the sound" isn't there to begin with, anything you do down stream is a waste of money. .