Help me choose an 1156 motherboard for my son's birthday

My P4 is getting old and I have decided to replace it. I will "confiscate" my son's computer and buy him a new one for his birthday. All we need is a new CPU, MB and RAM.

I will buy him either a an i3-530 or i5-750.

However, I am at a loss choosing an 1156 motherboard. What the main difference between a $100 MB and a $200 MB (please don't tell me $100   )

His video card is an HD4850 and I am not sure wether he will want to overclock or not his new motherboard.

What are the main specifications I should be looking for?

Budget is flexible but I would prefer to stay in the $100 - $200 bracket.

I get excellent service and prices from my local shop. As they mostly sell ASUS, I would prefer to buy an ASUS board (Gigabyte could be a second choice).

They mostly sell low end gears so I cannot really trust them for advice.