Well can I have more data, like your budget for instance?
I just built a HTPC a few months ago and I find that a HTPC and a Emulator build are almost exactly the same in there goals.
> Low Power
> Quiet
> Small
> Cheap
> High Storage
> No need for high end GPU
This is my forte, I came to this forum from the computer forums to learn about arcades, but I know all about computers

Let me link you my HTPC build, its OVERKILL for a emulator box with things like the 1TB hard drive but it was only like $300 so why not?
Build Log:
http://forum.desktopreview.com/showthread.php?t=235647Old Parts List:
http://secure.newegg.com/WishList/PublicWishDetail.aspx?WishListNumber=11010688As you can see from the parts list there are things there for my HTPC you do not need for a Emulator build.
You can easily cut out the remote control, and wireless card, and you can get a smaller hard drive.
This build is amazing, its very powerful, the IGP is one of if not the best, and its silent and uses very little electric power.
You can kick off even the case if you want, just mount the motherboard to the inside of your cabinet, but then you have to buy a power supply still wich is included in that case.
If you were bulding a gaming rig id go Intel parts but for HTPC or Emulator AMD is the way to go since they offer the cheap low power hardware and also have better IGP options.