The issue with most websites that have this kind of info is; they relate to general-purpose computer use, and audio is another beast
http://duc.avid.com/showthread.php?t=238426
this thread, while a mile long, has maybe the best collection of details that are relevant to what you are asking. I would read the first page or two, then skip to the last few pages for the most up-to-date additional info. It also includes links to tweaks and BIOS settings.
A few things to remember as you go wading in this pool
; motherboard/chipset/cpu choices are crucial. Assume nothing(like, if cpu A is great, then cpu B from the same company must also be great)
Pay attention to the chosen motherboard's RAM configuration. IOW, if the motherboard offers "quad channel" RAM operation, you want 4(or 8) identical sticks of RAM. If its "triple-channel, then its 3 or 6 matching sticks. If its dual-channel, then even numbers. but ALWAYS matching sticks.
Using a good SSD for a system drive will give MUCH snappier performance(Samsung 840/850 models are king of this hill)
Don't skimp on power supply(these days, 750 watts is probably the safest minimum). Buy "right" and you only have to buy once
There are many tower cases on the market, but I am very partial to the Antec P280(under $100 on eBay). This case is pretty quiet and quite roomy inside.
If you shy away from all this, pro-tools-pc.com is a great source for a really good PT machine at a fair price
Or, do what I did and copy a known great running rig. It may not be the latest, but it runs PT11 HD/Native like a champ