Geoff's already answered the shielding issue. I'd defo give the Diamonds a go and see what you think.
What I've found though is that correct placement of speakers is even more crucial in an AV set-up, than a 2-channel one, simply because you've got more of them to consider (and integrate correctly). In that respect, distance (to the listening position) and levels are also crucial. You really need to run things through a good home-cinema amp, and use a calibration mic, to get all that right.
The other thing I've found, if you really want to get everything sounding as seamless as possible (achieve sonic synergy), then it's best to use speakers all from the one manufacturer, as they'll have been 'voiced' the same way, and so the end result you hear will be more cohesive, musically and otherwise.
That's also one way of successfully integrating a centre speaker (in my case it's identical to the fronts), so that its output blends correctly into the mix, without adversely drawing attention to itself.
Get it all right, however, and the results can be sublime!
Marco.