Build the Perfect HTPC
More of a high level summary, but still not a bad place to start if you're interested in building your own HTPC. They list the pros & cons of several component options, and may help you narrow the decision making so you can stop thinking & actually buy.
Make sure you do some research on all components you plan on purchasing in order to choose those that do tend to run silently. Everything from cooling to hard drives should be looked at and all play a role in overall noise levels. Stick to HTPC friendly components.
Read the rest here.