bI think 16gb might be a bit much, I'm not familiar with what you do but I have a hard time believing you need more than 8.
The thing with motherboards is basically more expensive motherboards have more power converter "stages", some overclocking aids, heatsinked power converter components, and more PCI-e slots. The thing is the vast majority of motherboards get away with much much less, and can still overclock just fine. If you're on stock air cooling you won't be pushing many boards to their limit (unless it's a very small board such as the DFI mini ITX S1156 board that is clearly meant for <90W processors).
For example:
http://www.newegg.com/Product/Produc...82E16813157241
That motherboard is a bit lacking in features, but it has a PCI-e slot, it's got 5 phase power which...works...and it is cheap.
http://www.newegg.com/Product/Produc...82E16813128473
This board is 6 phase, has 2 x16 slots, and looks pretty good. I've never been let down by Gigabyte personally.
Again with the GPU, GTX460 is currently the nVidia chip with by far the best performance/price ratio. It is less than a 550Ti or 560Ti while providing most of the performance (not that big of an architecture change, think of the 5xx series more as what the 4xx was supposed to be, except they kinda messed up), and can be found for <120 dollars for the 1GB version. You'd be hard pressed to find a better deal than that, and it is a rather powerful card.
I think most HDD these days are relatively fast, but I heard very good things about the Samsung Spinpoint F4(?) drives. I have a WD 500GB Blue drive that is not even considered fast, but I find it plenty quick. If you can spare a little cash, get a small SSD (like 40-60GB) to put applications on, and that will speed up your overall computer usage experience. I wouldn't say it's necessary though. Recertified drives are incredibly cheap, like this:
http://www.newegg.com/Product/Produc...82E16822136742 (black is the highest performance line besides velociraptor).
If it were me getting a new PSU, I'd get something better than a Corsair CX, because I'm a bit skeptical about those budget PSUs having heard a lot of bad stories. I realize they are quality PSUs, but they have rather low efficiency by today's standards and the cheap price puts me off a bit. If you read PSU reviews like on johnnyguru, the trend seems to be more efficient => better quality and power characteristics overall. You're also paying your own electrical bill, and with a quad core + modern GPU that thing could be sucking a considerable amount of power. Getting say an 80+ silver rated PSU could actually make a difference. Going from 80% average to say 87% is >1/3 reduction in wasted energy, but going from 87 to 90 will cost a lot more and make a smaller difference. As for capacity, I wouldn't go over 600W, excess capacity is just extra money to the manufacturer's pockets and poorer operating efficiency for you. Midrange video cards use 150-200W, that CPU uses at most 150W when heavily overclocked, and everything else barely draws current. With a 500W PSU, your computer at full load falls right into the sweet spot for power consumption at about 300W, 60% capacity is when power supplies tend to work the best. But if you want to reuse your old one, that's good too, saving some cash.
http://www.newegg.com/Product/Produc...82E16817703026 <-- that for example, is a pretty good deal. 70 bucks for a 650W high quality PSU is pretty nice. I think you can get it for 60.99 since there's that 10% promo or whatever. If I were building a new PC I'd jump for it.
So like, 60+220+90+60+120+70? is 620, not too bad. I think you can do without the SSD for now.