As someone who has built hundreds of custom PC's, I will at least share my opinions about the Enthusiast's PC list.
Motherboard: an appropriate choice, but of course there are many options within that spec and price range that are suitable, but that range is the important thing
Processor: an excellent choice for most users, although the K-revision is only for overclockers
Memory: G.Skill DDR3-1600 is ideal for that system, and 8GB is sufficient
Graphics: similar to the motherboard - an appropriate choice that reflects the general video price range
Sound: debatable if a sound card is needed for even enthusiast, and the pci issue was mentioned by someone else, however this is a good price range for the inclusive Xonar, so it works
Storage: would suggest a (sync, if possible) 90GB SSD near that price instead; 1TB is a sufficient choice; tough category to select at the moment as prices scale quite a bit
Optical: would likely ditch the iHAS, the LG is quite capable. I do have a configuration like the one suggested and find it's more of a luxury, $20 is $20 in a tight build
Power: sufficient choice, again, it's about price range, and this hits it nicely; I'm fond of the 650W offerings, the better quality supplies can run CF/SLI comfortably
Case: I feel you can do more for less, the NZXT Phantom for example is regularly 100-130, there's the Tt Overseer (if ugly), etc. ~125 is a more suitable price range.
Monitor: some people love their big monitors so I can't really talk this down, but for me, I'd either save money and go with a higher quality 23", or even better go with two 23" for the same price.
Speakers: go with the cheaper Z-506. As for headset, there are tons of options for less money, but that's the problem here - people are strange about sound, esp. headsets. You're in for either the 20-40 range, or more likely the 100+ range, so finding a comfortable middle ground is tough; in that respect, your choice reflects this problem, although for me the headset is secondary and therefore a solid $40 set is the best match for all but serious music appreciation
Peripherals: okay, okay, I'm partial to Razer (my list would have Abyssus + Arctosa), and their entry-level stuff has people eyeing the $40ish range for both keyboard and mouse; but the two choices listed are suitable for gaming even if paying a bit more for those married to Logitech
Overall, not a bad list. As someone who deals with people on budgets, I'm used to tightening lists at all levels. I think fundamentally an Enthusiast PC should be in the $1500 range (not including some headroom for personal preferences), and I think that's doable here with some changes.
