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I don’t want to add a sub because this system needs to play as big as possible but have a SMALL form factor."
So why not get a small sub. A sub will far outperform any speaker you're considering in bass extension and output. And you like your current speakers, so you get to keep them. One of my requirements is an unobtrusive sub. I have two Paradigm Seismic 110 in my main system. And two Sunfire True Super Jr (9" square) in another. No one even notices them. You don't need a subsonic sub for music, even though the Seismics are plenty powerful enough for movies. Heck, I've got a Velodyne MicroVee (another 9" box) in my bedroom and that's powerful enough for me. It's tiny. Goes well into the mid-30Hz +/3 range. The other advantage is you get to place them in an optimum position for your MLP.
So why not get a small sub. A sub will far outperform any speaker you're considering in bass extension and output. And you like your current speakers, so you get to keep them. One of my requirements is an unobtrusive sub. I have two Paradigm Seismic 110 in my main system. And two Sunfire True Super Jr (9" square) in another. No one even notices them. You don't need a subsonic sub for music, even though the Seismics are plenty powerful enough for movies. Heck, I've got a Velodyne MicroVee (another 9" box) in my bedroom and that's powerful enough for me. It's tiny. Goes well into the mid-30Hz +/3 range. The other advantage is you get to place them in an optimum position for your MLP.