The Intel DH67GD board (review) is a better choice for HTPC. It should be more power efficient, it has an Intel NIC and it has a CIR header.
You can get away with as little as 2GB of RAM. However, try to get a 2x2GB kit because the pricing is not much more and it will add a little bit of performance.
The heatsink you found appears to only be LGA775 and the G620T is LGA 1155. You may want to consider one of the HDPlex chassis options.
