I had the JBL 580 awhile ago so my memory is pretty fuzzy on them. I have the Ascends cmt340se2 now in the basement and am using one as a center in my main system.
They will have a wider horizontal dispersion and are more efficient, great directivity for EQ. You absolutely need a sub(s) though.
All that said, I prefer the Revel F35/36 that you can pick up for the same price as the CMT340 with stands, strictly because my system is dual use and I like the option to run my mains full range for some music.
If you're itching to upgrade, go a little higher in the Ascend Acoustics lineup and get the LX's. They are the speaker to beat at $1500, I would take them any day over the Kef R3, Revel M106, Wharfedale Lintons and Wharfedale Aurua 2 I've had in the past.
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