If you are going to OC, you want a 3570k. That cpu has a unlocked multiplier and is meant for OC. You would want a Z77 board for that. Budget boards like the Asrock Z77 pro4 or extreme4 are priced pretty well (especially if you snag a good deal, they're frequently on sale). If money is not a issue, the higher end Asus or Gigabyte boards are pretty good.
For a 3450, I would get a H77 board. I got a Asus P8H77-V myself for it.