I purchased the Bose Acoustimass 10 series IV and a Sony 1015 Watts STRDH750 receiver, as well as a pair of Bose 161 for the front high surrounds. My question is this:

What's the best place to place the center speaker? Is it at the top of the TV (a 60" Samsung Plasma) or a the bottom of the screen?

I'm using all the included cube speakers with stands. Two at the sides of the TV (FL,FR) firing to the sides and the Surrounds on the rear to the sides of the main seating Sofa (RR, RL) (also firing to the sides).
I placed the 161 surrounds atop the sides of the TV and a bit higher (FHR, FHL) ( about 3 feet higher from the TV top edge and 2 feet from the leading edges). Both directly bolted to the wall.

I placed a second subwoofer behind the sofa (Sony) as well, firing to the side. The Bose subwoofer seats to the left of the TV cabinet firing to the front.

I bought the table stand for the center cube speaker, but I'm not sure what's the best place to place it to obtain the ideal sound for my surround system. Some plans I see online have the center speaker below the TV and others atop it.

What would be best with this system as set up in a 7.2 configuration? Should I buy the wall bracket for the center speaker and set it above the TV on the wall?

A note: For those wanting a 7.2 setup with the Acoustimass 10 series IV do what I did and get the 161 Bose surround speakers. They are a great match for this type of setup. You can use them either on the added rear back surrounds or as front high surrounds. I went with the front high surrounds as the cube speakers from Bose allow you to fire in two different directions from the same spot and thus negating the need for more speakers on the rear. The front high surrounds are great for sounds coming from above and feel realistic when sound flies above your head.

Is it worth buying some branded wire to substitute the wire coming in the box of the acoustimass 10?

I am going to purchases an Yamaha - 875W 7.2-Ch. A/V Home Theater Receiver and I was wonder if I could use the Acoustimass 10 Bose speaker setup with this receiver?

Would this system work well in a large size living room, 14 x 20 with a slanted ceiling going up from 8ft to 14 ft ?