so, go for something with a Core 2 Duo, and a RAM speed of 1066MHz or better, along with the above specs. MSI or Gigabyte make decent motherboards that support this.
i5 or i7 are overkill for what you are trying to do - possibly the i5 (if you want to go that way), as it's the successor to the Core 2 Duo (or Core 2 Quad) line.