If you are only using it as a HTPC and dont intend to play games on it go AMD, their IGPs are capable of playing back 1080p content, the intel IGPs are not so you will need a discrete card. For a HTPC there is no best intel motherboard, a P41 would do just fine.
Intel integrated graphics and HTPC don't really go together. Like hunter315 said, AMD is a much better choice for a HTPC. Their new 785G chipset is a very good foundation for a HTPC build. If you absolutely HAVE to use Intel, I would go with an Nvidia 9300/9400 chipset board.