My personal opinion is that the HTPC is very pricey. The one I just built (thread here
) cost about half what your build is going to cost and it's got MORE than enough power to do everything you mentioned wanting to do. As for the NAS, that's a wee bit trickier. To put this in perspective, I currently have three NAS units. Two 8-bay QNAPs (one backs up the other) and one 4-bay Netgear ReadyNAS (which is a redundant backup of the truly important files like family photos and tax files). I'm also looking to purchase another 4-bay NAS to keep off-site as yet ANOTHER backup. Now, I may be a wee-bit more paranoid than most, but there's a reason. I once had a computer die that contained a (then) lifetime's worth of work that was completely irreplaceable. Since then, I've made sure to live by the old Navy Seal code of, "If it can fail, it will. If you can lose it, it’s already lost. Two is one and one is none."
What I'm trying to say is, you will never, EVER have enough storage for all your files, or enough backups of your files. If all your files reside on a single drie (or NAS) then a single mishap could destroy everything you thought was safe.
In that light, I would strongly counsel you to spend a bit less on the HTPC components and a bit more on the storage solution. In fact, if at all possible, buy a larger NAS and also another, smaller NAS to BACK UP THE FIRST!
Remember, a NAS is redundant, meaning it can survive the failure of one (or more) of it's hard drives. It does not actually back up the data so if the NS dies you may be SooL.
/stepping off soap box