Well overall i think it is very nice.... especially for a first guide.
However, there are a few minor problems i see:
1. You tend to insert a bit too much opinion into your advice. A little is good but "The Beast" systems should include SLI and what not, no matter if you think it is worth it or not. Also a short explanation or a link to the video forums for those who dont know what SLI is would be prudent.
2. You say mature, meaning the product has been out for a while. While that can be true, most of the time people are referring to the manufacturing process which the chips were made on. For instance Intel has reduced heat output and power consumption on their lateest series, despite adding another mb of L2 cache, this is because they have become increasingly efficient in manufacturing the processors. Not necessarily how long it has been out. For "the beast" system you should definitely include an Nforce 4 based system. No doubt Nforce 3 is good but Nforce 4 has hit very very few speed bumps along the way and is doing well, mature or not.
3. Just "The Beast" system in general. The Pentium processor you picked is not at the highest end. Additionally you are still using basic value memory. While there is no speed differences by going to value memory, the higher quality memory does OC much farther. If you are building a system such as that most likely you will be overclocking. Also you should not recommend XP Home, XP Pro is much more worth it. Overall you justr need to step the level up. You are being too modest in configuring these system. If you are going to call it they highest end system, then give it the highest end compoents, worth it or not. If they want more bang for their buck yet still want speed they can choose the high end system and not the bleeding edge system.
4. Take Kingwin off of the Quality PSU manf. list. Although i wouldn't quite put them at generic they are definitely not quality.
5. SVC is also a very nice and trusted retailer to buy from.
SVC (Silicon Valley Compucycle)
6. X-bit labs is a very prominent reviewer as is HardOCP. I would definitely include them.
7. Your opening comments before you recommend the parts for a particular computer configuration need some work. For example, under basic computers you have
Would be good for basic functions and will run some older games
You shouldn't be recommending a 5200 for that price point. For another couple bucks you shouldn't have a problem finding a Geforce 4 or a 9600Pro or something. With those video cards you should be more than capable of playing all older games and most newer games at decent detail settings.
8. I know i have said it but i cant stress it enough. For the higher end systems you are skimping way too much. Although a 420Watt OCZ could probably power almost any system out there, for a "beast" computer people do not care, they want the best.
9. Ditch the Tt cases. I would say stick to Lian-Li, Antec, SIlverstone, and Coolermaster. However, i wouldn't see anything wrong with recommending the Tt Tsunami which is a very nice case but not for high end and "the beast"
I know this seems like a lot of suggestions, and i do not intend for it to offend you because in reality it is an extremely well put together guide and i applaud you for all the time put into it. I also would like to say i realize it is for new users but you still have to recommend things like they were an experienced user, basic definitions yes, basic explanations yes, but do not skew the reccommendations because they are new.
Keep up the good work. Excellent thread.
-Kevin
Edit: You might want to either take out the poll or include an option that reads "excellent guide, but it could use some work in a couple of areas" or something that means that you dont have to have learned something to post in this thread but that you just want to congratulate.