might be a fair bit more but will generally play games at near max settings. also, either get a full 128gb SSD or just dont get one. 64gb ssds have very low value and dont perform well
7870 is the best bang for the buck right now. 2 7770s are around 7950 performance, which a 7870 can reach after some overclocking.
550w is enough for a single 7870
a 3570 is not much faster than a 3470