Re: barebones kit
PCI-e interface utilizes modern high performance video cards. Make sure the video card specifically states that it's used for PCI-e. Dimms are common memory interface. Intel use DDR and DDR2 while AMD currently use DDR, but DDR2 is coming for AMD compatibility. The more Dimm slots, the more RAM you can upgrade. Plus, new chipsets support dual channel memory support for better performance.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?