3-6 dB increase is about all you can expect.

I agree about the SPL meter. Get a handle on how loud you are really listening.

If your speakers produce a "strained" sound, you might have a receiver problem.

You might benefit from the upgrade. If your speakers sound clean and tight at your levels, you're probably fine.

If you have upgraditis bad and you must have their best speaker and new amps......go for it!