I'd say closer to about 700w and that's around $80-90. Not strictly more than any other system component.
This too. A quad-core is more than enough for most games, and even a processor like an i7 is a bit too much for gaming. A decent i5 is all you really need to avoid any bottle-necking with...
Total price under $2000 is not difficult at all. Check out this build.
Intel Core i5-3570K, MSI Radeon HD 7870 - System Build - PCPartPicker
I picked out the parts quickly and you may not need something this powerful (or perhaps you need something slightly more powerful), but a PC with these...