I think i'm going to get the 3570. I won't get a new mobo, but when I do, which will be soon, i'll oc it.
But I'd say get a Bigger screen. You'll not enjoy much in that resolution.
But getting a 3570k over 3470 isn't worth it until you OC it to 4.5 Ghz (You'll get 5-10 fps in CPU bound Games)
If you have the Money then get i5 3570k with Z77 Mobo.
3570k will be future proof and will be better in Softwares.