My personal recommendation for CPU is and has always been AMD. Unless you have a massive amount of cash to blow, you'll never go bleeding edge. While AMD has made great strides in advancing beyond Intel, the pattern of Intel coming up with a design and AMD improving upon it and being significantly cheaper has held true for decades.
Multiple CPU cores are wonderful for those who do heavy multitasking, but there's a limit to how many cores and/or CPUs an individual needs. Running multiple CS3 apps at once, you need the extra cores (my counterpart at work for example, a graphic artist, runs In Design, Photoshop and Illustrator all at once opening catalogs full of hires images. She brings her dual core iMac to it's knees)... Otherwise stick with dual core and go for higher clock speed.
Obviously, cram as much RAM into the system as you can... You WILL need it.
As for the motherboard and video, I suggest going with an all nVidia solution. Components designed to function together for maximum efficiency. It's hard to find any video card without dual monitor capability these days.
Hard drive, the faster the better, stick with the main brands and go SATA. Were it me, I'd get a lower capacity (60GB or less) 10K RPM drive as your boot drive with a high capacity (500GB+) 7200 RPM storage drive. Between boot times and memory swapping, you'll be glad you did.
