If you have the money to go for i7, by all means do so but as far as XIV is concerned i5 = i7 when comparing same "range" models.
i5 750 + GTX470 here, 1920x1200 @ CSAAx8 Everything Highish without AO/DoF and I manage capped FPS everywhere but a very few places, in which case it's more like 45 FPS which isn't really a big deal.
I can run 3 FFXIV instances at 1280x1080 with capped FPS too, haven't really tried more.
XI Wiki






