I was listening to the SACD version of the 1812 Overture, in 2 channel, with the L890s in the main room, w/o any subs. They did a good job of reproducing the canons, of coarse, not to the db level of the subs. Just a "slight difference of power", 220wpc compared to 800wpc. The overall sacd recording came across very well thru the L890s.
I looked in the manual but it didn't say what size the spike threads are.
Your experience in buying the displays reminds me of when I bought the displays in '79. No boxes, no manual. Why can't these clowns at least keep the manuals in a file cabinet.
And Frys sales staff could use a lesson or two on audio as could the guys at Magnolia HT, here.