Check out the Pinpoint AM40 mounting brackets from Crutchfield. I use these to mount 4 Paradigm Studio 20's. They are bullet proof and look very nice. They are solid steel with an attractive plastic cover. If you mount them into a stud in the wall, I think the 50lb rating for them is conservative. My Studio 20's have mounting screws imbedded on the bottom of the speaker that are threaded. I used them with an inexpensive metal strap I bought at the hardware store to insure that they don't vibrate loose and to avoid drilling holes in the speaker. They come with foam tape to put on the mount to avoid scatches on the speaker.
Onkyo TX-NR5009 Used as PrePro, Outlaw 770, Oppo BDP93, Marantz TT15S turntable, Paradigm Studio 60's main, Paradigm Studio CC 590 center, Paradigm Studio 20 surrounds, Paradigm Studio 20 rear surrounds, Pair of Paradigm Servo 15 subs, Sharp LC90LE745U 90" display, Auralex room treatment