Step aside, step aside, this is how a newegg employee does it(we send out coupon codes for a reason).
Case: Rosewill challanger: 40$(better stock than antec 300)
http://www.newegg.com/Product/Product.aspx?Item=N82E16811147153
HDD: WD blue 500gb: 65$
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136769
GPU: XFX core edition 7850: 220$
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150617
PSU: Corsair Builder series 500w: 30$
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139027
Memory: Gskill ares 8gb: 41.40$
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231544
CPU: i5-3570k: 215$ (while i wouldn't suggest the i5k for your purposes, its on sale while the other comparable aren't)
http://www.newegg.com/Product/Product.aspx?Item=N82E16819116504
Mobo: Biostar TZ77XE3: 100$ (got good reviews regardless it came from biostar)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813138355
Now insert coupon codes as follows(requires login):
EMCNDHA27
EMCNDHB34
EMCNDHB222
EMCNDHA42
EMCNDHD77
Total: 741.33$ +30$ in rebates
This is gonna leave you with abit extra money. You can either bank that, put it into a larger hard drive, put it into a ssd boot drive, put it into an optical drive, a cpu cooler for ocing, or put it into a better video card.
Regardless, this build shits on all the other suggestions and I'd love for them to tell me otherwise. It's all for the op as far as i'm concerned, this is gonna be the right build, but maybe just a few tweaks.
Edit: if you srsly consider other builds over this one, well, I'd feel horrible that such an opportunity was missed. I srsly want other posters to consider this over their own suggestions, say which they'd prefer.
Edit Edit: I did like 3 edits to this post in the last two paragraphs, feel free to read them again if youre coming back.
Edit Edit Edit: What you could add to meet your budget or get closer to it
CPU cooler:CM Hyper 212: 20$ (will let you take advantage of the i5k overclocking ability)
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065
GPU: MSI twin forza 7970: 280$ (would replace your 7850)
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127662
DVD Burner: LG DVD burner: 17$ (i dont use optical much anymore)
http://www.newegg.com/Product/Product.aspx?Item=N82E16827136247
SSD Boot/ISRT drive: OCZ vertex 3 60gb: 55$ (intel smart response is amazing and available on z77 mobos)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820227737
Edit (4x): I do my best to avoid mail in rebates, as evident in the first build. I suggest you avoid them aswell when you can.
Edit (5x): Might aswell do some closing thoughts on the build anyway. As I said to the first poster, this is a lopsided build, but that is only because the current sales/market dictate this over other solutions. In all honesty, this would be a great build if you planned on upgrading in the future. It is easily capable of powering 500$ graphics solutions so if now, or in the future, you want to throw in either a gtx 670 or 680, it will do just fine. I5k should offer you some ocing potential(again) and you'd have to be rather thick not to fiddle with it. 500gb HDD is meh, but SSD prices are plummeting, for all system builders i'd suggest getting the cheapest storage solution too simply buy you time untill a full ssd system becomes viable. Memory is quality stuff, it could benefit from some oc aswell. The case is banging, no need to buy extra fans. People are gonna complain about the power supply(its non modular, its low wattage), but mid tower cases have plenty of room to excess power cables, and pc component power requirements are going down, if it powers what you have right now, it will power everything in the future aswell(excluding enthusiasts).