A lot of responses you're going to get will be from fanbois, of one persuasion or the other. I currently own an Intel i5 (2500k), but it was bought SOLELY for its gaming potential. I also own an older generation AMD (Phenom 2 955) that I use for EVERYTHING else. I, too, use it for photo work, but it can sometimes be quite extensive. I use Photoshop CS5, and the AMD handles everything I throw at it, with nary a complaint or hiccup. It's a real workhorse.
People telling you that AMD is cheaper for a reason, are the same ones that would tell you Android is cheaper for a reason. I wouldn't go so far as to call this a Chevy/Ford debate, because each processor has it's advantages. For what you're going to use it for, stick with AMD. You won't be sorry.
Also along with what netsiu is saying above, is about ram (onboard memory). It is becoming increasingly cheap, and honestly, you should buy as much ram as you can afford, or the max that your system's motherboard can use, whichever is lower. I, too, build my own systems, so buying a pre-built machine will definitely limit the amount of ram you have, at least initially (you can always add more at a later date). However, when shopping for a new computer, pay attention to the amount of installed ram, and factor that into your decision.
Also, since you aren't going to be playing any games, your choice of video isn't really THAT important, since onboard video will work. It may not work as well as a stand-alone card, but it should be sufficient. However, should the need arise for something stronger than onboard, for your needs I would suggest an Nvidia card.
Almost all of the newer Nvidia cards will have CUDA processors. This is important, as many photo or video processing programs can use these "CUDA cores" as extra processing power, thus enabling your project(s) to finish more quickly.
Note: This post was edited by its original author to merged two post by letgoofmyears into one. on 04/20/2012 at 4:08 PM PT