If you choose to upgrade electronics (not a recommendation to do so, but...) I would look at something with Audyssey XT32 as the room correction. Many of us seem to be in agreement that, while not perfect, it works well enough, especially with the Audyssey App. Denon 3500 has it, not certain about the Marantz SR501x series (601x does.)
To stress, the electronics will not really offer much improvement unless you are upgrading from, say, very inexpensive 10+ year-old gear to something retailing new around $1K. That Denon 3500 is a great buy right now, for example. (Still not a recommendation!
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In order to increase SPL by any noticeable difference, you need a doubling of power. That will only result in a +3dB gain.
In order to have a system that plays loud, you would need speakers that have a higher sensitivity. Also, speakers that can handle greater power will aid in that quest.
While the ELAC speakers have a reputation for good sound, they do seem to also be known to not play as loud as others.