GPUs really dont care what CPU you pair them up with as long as its strong enough, there is no benefit for putting an AMD GPU with an AMD CPU, it will perform just as well with an intel CPU, an nVidia GPU will perform just as well with an Intel CPU as with an AMD CPU.
Competitors drivers dont conflict because they are competitors, drivers are per device, the chipset drivers will not interact much with the graphics drivers, now if you had an nVidia card in and then put in an AMD card without totally clearing the drivers then you have two sets of video drivers that can conflict, but with an OS like windows 7 you can actually run an nVidia card and an AMD card at the same time on the system so driver conflicts arent something you need to worry about too much.
Since most people have Intel CPU's, it would not be in AMD's best interest to not work well with Intel. Besides, almost every benchmark site you look at showing how the AMD GPU's work, put them on an Intel machine.
That said, if you did want PhysX, which be aware, there are only about 20 games that use GPU accelerated PhysX (not to be confused with software PhysX), you might desire an Nvidia GPU. AMD GPU's has better AA, however.