Originally posted by Anvh Motherboard is going to be the hard part, i would go for gigabyte or asus for all the branded things.
+1 on this. I usually use Gigabyte Mobo's
one important thing is to never skimp on the RAM - stitching panoramas, HDR and using layers in photographs eats up RAM - the more you have the smoother things will go for you, I exclusively use Corsir ram.
The videocard doesn't matter all that much - but depending on your monitor having HDMI and Displayport is essential - many monitors designed for photography these days are offering displayport connectivity and the reason for this is that is because the increase in channel bits.
Another thing is you may wish to have an external data back up system - I personally use a DROBO with Ethernet connectivity for secure backup.