Budget is around 500-600.00 for board, processor and memory. Less is better of course.
CPU:
Core i5 3570K = $230 - $15 off coupon EMCXVXR22 until Feb 11 = $215
^ On the CPU side, you could upgrade to i7 3770K if you do video encoding/rendering/serious multi-tasking. If you do gaming while streaming with xsplit, FX8350 could be a good option. Otherwise stick to i5/i7s.
Motherboard:
GIGABYTE GA-Z77X-UD4H =
$165
^ On the motherboard side you could go down if you want to say Asrock Extreme 4 or 6 (tons of features for the price). Alternatively, you could step up if you need more features like Thunderbolt (Gigabyte UP4-TH). If you are into serious hardcore overclocking, maybe spend more for MSI Z77 Power or ASRock Z77 OC Formula. Although, I'd personally rather downgrade to Asrock Extreme 6 and put the $ into a 128GB SSD or towards an i7 3770K than spend > $200 on a mobo. Alternatively you can get a $150-160 board and a
$40 Thermalright True Spirit 140 that would help you MUCH more than a $200 board and a stock Intel heatsink. Just make sure the 173mm clearance isn't a problem in your case. There are plenty of other CPU coolers I could recommend. If you aren't overclocking, you can save $ on getting a non-K series i5 and skip the after-market cooler. I would personally get the K series CPU since overclocking is so simple. Later you could learn it
Memory:
Crucial Ballistix Sport 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 1600 1.35V =
$84
G.SKILL Ripjaws X Series 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 1866 =
$99 - $20 off with coupon EMCXVXW78, ends Feb 7th.
^ Again if you don't do Adobe Photoshop or know that you require more than 8GB of RAM, you can cut the price in half by going with 2x 4GB sticks and take that $40 savings towards an SSD. An SSD is really a much more important upgrade than 8GB --> 16GB of RAM. But 16GB fits into your budget still.
Only caveat is Intel's next generation Haswell CPUs will launch around June 2-5th. I am not recommending you to wait but just letting you know that the 3000 series Intel CPUs (Ivy Bridge) are based on the 2-year-old Sandy Bridge architecture with minor improvements. So if you spend $500-600 now, I am just letting you know that the "next thing" from Intel is coming in June 2013 so that you are aware of buying near the end of this CPU generation. I obviously don't think it's worth waiting for though since you'd be without a computer!