i3 have 2 cores with hyper threading & better single single core performance but no overclocking capabilities and fx 6300 have 6 cores with lower single core performance but is very good at overclocking ....so go with the fx 6300 ..
yes but its high quality corsair cx is a tier 3 average psu if u want to go with corsair get the rm/tx/ax series but they will cost u more....the best brand would be seasonic..