You can use 1600 mhz ram with sandy bridge, I'm doing it right now. It will probably default to 1333 when you first install it, just have to change it in the bios. XMP makes it easy, just look for xmp ready ram.
slightly improved performance 5-10% due to new architecture, better integrated graphics, pci-e 3.0. doubtful you would notice any difference between the cpu's once they where installed in a system however, i'd just go with whichever was the best price. if difference in price was negligible/ivy was cheaper, i'd go with the i3 3220.
i personally would spend the extra $10 for the 200mhz speed bump & the increased performance (or at least the feeling of it) but it's relative - is the $10 more beyond your budget? would your rather put that money onto a different part, or are you happy to spend alittle more for a slight increase in performance. that's what matters.