I'm going to start this off by saying that I have minimal knowledge of how computers actually work, so I may not understand what you are talking about if you get very technical, but I'll try ny best to keep up.

I'm looking to mostly get the a desktop with 3D modeling applications in mind, such as ZBrush and MAYA, as well as Photoshop and similar graphical programs.  Gaming isn't really a concern because I mainly stick to consoles.

I am most likely going to be buying pre-made from best buy or some place like that, because I really don't trust myself to attempt something like that.

I've been looking at desktops with 8 Gigs of RAM and about 1 TB harddrive space, but the processor highly confuses me.  I went to the store and the guy there was recomedning one with an AMD Phenom II X6 for arounf $800, but on the website there are similarly priced towers that have i7 processors instead.  Anyone have preferences, thoughts, or can explain what some differences are?

I'm faily certain this is the one the sales person was showing me

Build your own one and make sure you have a top of the line graphics card (preferably Nvidia) and an i7 core processor. If you shop around right you could save yourself a good amount of money.