Get what is the cheapest for you. Sandy is slower clock to clock with Ivy but it can be overclocked higher than ivy-b to meet ivy's performance. From what I remember, a 4.5GHz ivy is a 4.7GHz sandy equivalent.
So yea, just grab whatever you find the cheapest, look for the motherboard review how it overclocks and you are set.
For the graphic card, I think the 7950 is a solid choice price/performance. If you were planning to go dual card, I would however go for nvidia. I personally think getting two cards is a waste of money with a single monitor. Better just upgrade next year than spending twice on a generation that will soon be replaced.
My best advice to you: no need to spend a lot, spend less to upgrade more. Every generation there is a 30% increase performance, after two generation your hardware is already worth nothing. My 5870 lost 75% of its value in 3 years!
Oh and for the RAM, if I had to upgrade, I would grab these:
They are mad cheap, overclock like champ and low voltage. I am waiting for the 2x8Gb model to change my sticks
As for the budget,
200-250$ sandy/mobo combo if you have the patience to find used deals
300$ 7950 http://www.newegg.com/Product/Product.aspx?Item=N82E16814125414&Tpk=gigabyte%207950
(3 games with it)
40$ Ram sticks
Total: 590$ so far, I suggest you to get an SSD this model is good and cheap:
There is also this model:
I stopped following SSD market long time ago. I prefer using MLC over TLC so my choice goes to the 830 series. I wouldn't spend more than 100$ for a 120GB ssd.
The hard drives are quite expensive, I think you are fine with your current 1.5TB.
You have 120$ left for a case if you need, a good cooler and some fans.Edited by Just a nickname - 11/9/12 at 12:19pm