Help with first gaming build <$900

Thank you all in advance for any help you can provide! I've been pulling my hair and agonizing over things that I probably don't even need to worry about for the past week and realized I really need to ask for advice instead of pretending like I know what I'm doing. I searched around in the forum already for something similar to what I'm looking for, but only found conflicting advice and/or advice that didn't match what I was looking for.

***

Approximate Purchase Date: Within the week

Budget Range: Up to $900 before rebates. Obviously if y'all think I don't need that much oomph for my computer, I would gladly pay less.

System Usage: light gaming, general web browsing and streaming, school work, some photoshop, music, and I've dabbled in 3d animation

Parts Not Required: I've got a keyboard, mouse, and speakers. I have a copy of 64 bit Windows 7.

Preferred Website for Parts: I've been browsing Newegg so far, but I don't have an actual preference. Amazon will work for me, or any other online retailers. Also, I work at Best Buy, so buying from them could be a good idea in some cases for the employee discount.

Country of Origin: USA

Parts Preferences:
I've been flipping between the intel core i5 2400, core i3 2100, and the AMD Phenom II X4 955. Everywhere I've read has the core i5 highly recommended at this time, but I'm not sure if my needs match the power that thing is capable of. Then again, I would like this build to last a while, so investing in the core i5 might be the smart thing to do.

Also, I've been more interested in Radeon than nVidia, but I'm willing to be convinced otherwise.

Overclocking: I don't have plans to, but I'm not against the idea.

SLI or Crossfire: No, I don't really think I need that extra complication. Again though, I'm not against it.

Monitor Resolution: 1920x1080

Additional Comments:
I'm planning on using this wall mounted monitor arm, so when I choose a monitor I need to keep this in mind.

I've been using my laptop to play games like Dragon Age 1 & 2, WoW (not playing it anymore though), Bioshock 1 & 2, Fallout 3/New Vegas, Oblivion, Portal 2, Witcher, and some old games like Baldur's Gate and various emulators. As you can see, I play mostly RPG games and some MMORPGs. I'll play most RPGs that come out in the future.

Since I've been using my laptop for these games, the poor thing has been pretty stressed trying to display some games at just medium graphics. It recently went into a coma trying to play DA2. That was probably was stupid on my part. In any case, maxed out graphics isn't a priority, just a plus. High settings are usually more than enough for me.

Additionally, I had some problems playing DA2 with the nVidia GPU the laptop used (the laptop went comatose before I could troubleshoot the problem, but from a quick google search it looks like it had something to do with nVidia and directx 11 not playing nice or something like that. Common problem from the look of things). I would like to avoid this.

I don't have any requirements for the case. Quiet, cool, and inexpensive are my only preferences; looks are only a bonus for me.

Again, thanks in advance for any and all help!

does the $900 include the monitor?

also, $900 is not too much for a gaming computer.

it is more than reasonable, just give me a few minutes and I'll give you an build

Try this:
http://secure.newegg.com/WishList/ [...] r=12113169
This is what I am going to get soon, but it should be good for you too.
My budget is $800
Ignore the fans and fan ports, unless if you get the HAF 912, then that would be great for you.

If you get the i5 2500k and a better motherboard (because you said you are not sure if you wanna overclock) then I dont think you will have enough money for a good 1080p monitor, but I can be wrong.

Good Luck

*also, that newegg list is for product reference, I am not going to get all of it from newegg.
The case and dvd burner is the same price, but free shipping on amazon
Be sure to first pick out the products you want, then do a quick google search and see where it can be bought for the cheapest, but pick safe website and be sure to check the store warranty)