Hey Tyler, I know you were asking for a prebuilt or to guide you through a custom order on ibuypower or such, but please take a second and consider what I'm about to tell you.
If you plan to be using or just gaming on computers for some time, you really should be considering building it yourself. I know it may seem like a huge monumental task, but it's quite manageable. There is nothing comparable to making your own PC in terms of quality and price. You know EXACTLY what went into it, because you're the one who put it in the case. It makes modifying your build later on easier too. Also, it's really not as hard as most people think it is if you just take the time to read the instructions. There's also tons of help online to be found if you find yourself with a question. Plus, it's fun! The only thing is you have to make that initial leap in deciding to make your first build. I cannot even begin to tell you how much I recommend you build this thing yourself.
Now second thing is I don't know why someone was recommending one of AMD's FX CPUs. They're simply not worth the money at any price point for gaming. I'm not an Intel fanboy by any means, but the reality is that Intel CPUs are king of the block right now at just about any price. Don't take my word on it though, take a look at this article and decide for yourself
http://www.tomshardware.com/reviews/gaming-fx-pentium-apu-benchmark,3120.html
Anywho, assuming you decide to take my advice and build your own, here's a start for you.
Part list permalink:
http://pcpartpicker.com/p/4iV3
Part price breakdown by merchant:
http://pcpartpicker.com/p/4iV3/by_merchant
CPU: Intel Core i5-2400 3.1GHz Quad-Core Processor ($149.99 @ Microcenter)
This is one of the best gaming CPUs on the market now. It's only Achilles's heel is that it doesn't have an unlocked multiplier for overclocking. Really though, I can't see that being a big need for you.
Motherboard: ASRock H61M-VS Micro ATX LGA1155 Motherboard ($54.99 @ Newegg)
This is a very bare bones motherboard. You might want to chose a new one if you want to the ability to overclock, USB 3.0, Sata III, or are interested in crossfire/SLI in the future. If you're not interested in any of those four things, this will do you nicely. If you are interested in one or more of those, just say so and I'll help you find one more suited to your needs.
Memory: G.Skill Value Series 8GB (2 x 4GB) DDR3-1333 Memory ($36.99 @ Newegg)
Basic low profile RAM. You will definitely not be needing more than 8GB. Truth be told you could get away with 4, but since it's so cheap, why not?
Hard Drive: Samsung Spinpoint F3 500GB 3.5" 7200RPM Internal Hard Drive ($98.99 @ SuperBiiz)
Hard drive prices are crazy, so a lowly 500 GB is what I recommend. If you could get away with less, I would suggest a 320, or 250 GB to shave down the price.
Video Card: Sapphire Radeon HD 6870 1GB Video Card ($152.55 @ Newegg)
A pretty high end graphics card. It should run Diablo 3 quite nicely on high settings.
Case: Cooler Master HAF 912 ATX Mid Tower Case ($44.99 @ Microcenter)
A good solid $50 case. Any case at this price point with good air flow will do though. Antec 300 is another popular one. Just take a look around on newegg and find what you like.
Power Supply: Antec 500W ATX12V / EPS12V Power Supply ($49.99 @ Newegg)
This will give you more than you need in power, with a pretty good efficiency rating too.
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($27.97 @ Newegg
Any optical drive would do honestly
Operating System: Microsoft Windows 7 Home Premium SP1 (64-bit) ($99.99 @ Newegg)
Total: $716.45
(Prices include shipping and discounts when available.)
(Generated 2012-02-02 13:45 EST-0500)
I left a little wiggle room in the budget in case you live in a state with an online tax, like me

. If not, we can put some more money into the build. Like we could step up the graphics card and powersupply, a better motherboard, or an unlocked CPU.
If you decide you must absolutely have a prebuilt, just say so and I'll go through an ibuypower walk through with you. Please give the build it yourself option some serious thought though.