Actually, several things are wrong but where is the main issue?
I replaced an all in one Sony set up with a Sony DN840 AV receiver and Kef 1005.2 speaker set. It worked ok, but no punchy wow factor. I used an old pair of Totem dreamcatchers as the front left and right speakers. It was better, and then got a deal on a Focal centre speaker. It got better in some ways but feels unbalanced.
The Focal centre is very dominant even after trying the Sony auto speaker setup program or trying it manually. The rear surround speakers are too quiet but probably lack depth more than anything.
My guess is
1. Mixing speakers is a problem because the receiver has common settings to all, and I have speakers that want different bass and treble balances.
The cure is:
1. Get a receiver with more adjustments.
2. Replace the remaining Kef 1005.2 speakers (still used as rear 4 in my 7.1 arrangement) with something a little more substantial.
Unless someone has any other great ideas.