If you're overclocking go for the 530. The multiplier isn't going to open up that much headroom unless you're going for the limit, and the i3 530 already hits 4ghz on stock or near stock voltage.
As far as the motherboard, you'll be paying a little extra if you want a good 8x/8x mobo.
$190 Asus P7P55D-E
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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Budget: Notice this is a micro ATX, meaning you'll have less PCI slots, less room, and probably more heat. (luckily this motherboard has features like a standard motherboard, ie: lots of SATA/USB/RAM slots)
$140 Gigabyte GA-P55M-UD4 **MICRO ATX**
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
16x/4x are going to be much cheaper, and TBH could run up to 5870 crossfire decently, according to this.
http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Expr...
However, if you plan on getting something much stronger than a 5870 in that 4x slot you'll run into issues.