Since JiminDenver mentioned me, I'll give my $0.02 worth, even though I had 1141 bulbs, not 921. Only the adapters are different.
I like the warm white 36-1210 panels from 2011_led, AKA duan_led2010.
ClickyHe also has packages of 10. See his store
I bought some 36-1210 from another seller and found they were much dimmer, warmer light and much poorer quality. Unfortunately I don't remember his name. They were cheaper too.
As Jim said I have fixtures with frosted lenses that disperse the light from the panels. The surface where the panels are attached is plastic and I found that gently sanding the area made the panels stick very well to the fixture.
Hope you find lights you like.