any favorites on specific parts that you like given my needs?
Lets try to be more specific.
Small form factor (as small as possible), black/dark metallic in color
Silent (very important)
No gaming, no live tv, no optical drive
I would probably go with the Antec 110, specially since you want as cheap as possible and small factor, and you dont have a need for optical. But if complete silence is more important, then H3 would be my pick, but at 4x the price.
Will be running a suite of usenet applications (therefore want it powerful enough to be able to handle the extraction and par file repairs without compromising video/music playback)
Will be used to watch common formats up to 1080p of movies/tv shows/music (ideally have connectors to have choice whether or not to connect to amp)
Depends on what and how, all Sandy Bridge and Ivy bridge built in gpu, can handle 1080p playback, so my suggestion is to with Ivy Bridge and chose depending on the load that other apps you using. For pure playback and on a cheap setup, i would just go with Intel Celeron G530, can be bought for $50 and an Intel mobo, H61 or H77 mITX, depending on how much you want to spend, and what outputs you need.
Be able to handle streaming video[/list]
Here is probably the most important thing you need to decide, live encoding/decoding can take a lot of cpu, depending on the software and how many at the same time. Check the software you will be using and decide on the amounts of streams you will have running at the same time to decide on what CPU will be best for your needs.
Personally i find best to build cheap htpc like H61 mobo + G530, and have the server be a pure storage center and let the htpcs do the rendering. But this is up to each and your needs.