For scraping Movie files I've been using
Media Center Master and it works really well. I cannot find a good guide for use with TV shows though which is a pita. Media Center Master does not play nice with my TV shows unfortunately.
What I did was I loaded my movies folder in Media Center Master and sorted all the metadata for each movie and then set it to rename the folders & files to show as "Movie Name (Year)". Then I added the main movies folder to MB and all is well. I also like that Media Center Master allows you to group things by collections such as my dark knight triology and james bond movies.
Right now I have 1.5 TB x 2 for my storage and that is over 50% full and thats not including the 500 gigs of tv episodes I have on my 1 TB HD. In addition I plan on ripping a bunch of blurays so I think the 4 TB would be my best option. I may just settle for the 3 TB and if it becomes an issue upgrade later down the road.
One thing of note is the case that came with the PC only has spots for 4 HDS, it is a mini-itx case so I'm sure that will be CRAMPED. In addition the motherboard has only 2 x SATA3 and 2 x SATA2.
My understanding is that even modern day HDs have trouble maxing out SATA2. I plan on putting the WDs on the SATA2 and my SSD for OS on the Sata3. I think that will give me the best performance and is the best setup.
I am excited to have a dedicated HTPC now just for the stuff to come in and get my butt in gear .