The center is pretty good. I've got no issues with it.
I would be using 4 NS-F310's and 4 NS-B310's. F310's for front and rears, B310s for front and rear presence.
I've been looking for better for less but haven't found any.
I would like to have all 9 speakers from the same series so this limits my selection.
I'm not against replacing the center...
"No one listener, therefore, can be the arbiter of absolute quality."