1000-1500 Gaming Build

Hi,
So I'm looking for a good gaming build. This will be my first build and I'm obviously looking for as much advice as possible. I need everything. I currently own a Mac, and have no keyboard, mouse, monitor, nothing. So this is the works.

Purchase. Next 1-2 weeks.

Budget. 1000-1500, I would like to stay as close to 1000 as possible, but no more than 1500.

System Usage. This will be used purely for gaming. I have my iMac for all other uses. I've been leaning towards an i5 because of this.

Monitor. Yes.

OS. Yes

Website. Don't care. I've been primarily checking Newegg.

Location. Chicago area

Parts. I've been primarily looking at Intel CPUs. But I'm more than open to AMD if it's a better build for the price. In terms of GPU, no idea. Honestly, I would just be taking a shot in the dark if I bought a GPU currently.

Overclocking. Maybe. I have no experience with overclocking, which scares me. But I have some friends that do, and I might get them involved. I've researched superclocked GPUs, but I'm less than thrilled with the idea of paying for overclocking, seems like cheating, and a waste of money.

SLI or Crossfire. Probably not. But if it can fit within the budget, why not have the option.

Moniter resolution. As stated before, I need a monitor. I don't want overkill with whatever GPU I get, obviously.

Additional. I really like everything in terms of gaming. So I'll be running BF3, Diablo III, Borderlands, etc. Pretty much anything but WoW. (I'm not willing to subscribe my life away to Blizzard.) I've done some research, compiled some info for savings, looked at pre-build sites, but I'm looking for as much input as possible.

Why. Peer pressure.

Huge thanks in advance.