That's easy. 1500's enough for basically top-of-the-line everything.
http://www.newegg.com/Product/Product.aspx?Item=N82E16827106289
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129021
http://www.newegg.com/Product/Product.aspx?Item=N82E16824236047
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102872
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.323094
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.322821
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.315058
Comes out to 1410$ with shipping, after mail-in rebates. That's basically what I have in front of me right now, you've go the most powerful single-GPU video card on the market, great CPU, tons of HDD space, huge monitor, and so on.
Obviously, if you wanna cut down from that, there's plenty of room for you to go down a lot. You can probably cut down on how much you spend as well by getting different combos and rebates, I threw this together somewhat quickly. =\
Alternatively, you could spend a bit more money and get an i7 as well, just swap the CPU/motherboard combo there for this:
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.315584