Looks like I'm late to this party and I just skimmed the thread, but I'll try to interject some points that I don't think anyone else covered.
Re: graphics cards...this is tricky. There's nothing preventing you from running PhysX on an AMD card. However, PhysX is owned by Nvidia and they put little checks in their PhysX drivers that only allow GPU-acceleration on Nvidia GPUs. This yields better performance & in a lot of cases enhanced PhysX effects in your games. Another consideration outside of games is Cuda. That's an Nvidia exclusive as well & if you have any software that takes advantage of Cuda acceleration you might do well to consider Big Green.
However, things aren't so bad on AMD's side of the table. Per dollar spent you usually get more horsepower for your money with AMD & their cards are definitely more power-efficient than Nvidia's. AMD's cards handle a few esoteric video formats/codecs better than Nvidia as well.
If going with an Intel platform new chipsets are coming out touting the new PCIe v3.0 standard which are promising optimized data pathways for greater throughput. You can find this new standard in the new H77, Z77, and X79 chipsets. While PCIe v3.0 won't future-proof your new PC it might in the long run help you get a greater life-span out of it.
Now as for monitors, go big or go home. Try to find something with the ever-increasing more rare 16:10 aspect ratio. You won't notice much difference if watching movies at your desk, but you'll really value the extra screen space when you switch gears to productivity software.