1) Visit
Silent PC and go to their forums. You'll learn everything there is to know about which fan to use, which PSU to use, how to undervolt your case fans, etc. etc. etc. Basically, how to get your computer as quiet as humanly possible.
2) Yes. AMD's are typically faster for the price. That is... if you buy a $100 AMD processor, then you're going to get a much faster CPU than if you buy a $100 Intel processor. If you want the absolute fastest that there is, then right now, you'd wanna go with Intel (P4 3.2GHz and Canterwood chipset.) But if best-bang-for-buck is your goal, then go with AMD. Make sure you pick the right chipset, though. For example, Nforce2 is the fastest chipset for AMD CPU's, but there are compatibility problems that have creeped in with some audio programs. But VIA KT400 chipsets are pretty much on par with Nforce2, and when coupled with DDR333 RAM, they perform pretty much just as well but at a lower price poitn and with less compatibility issues. So you gotta get to know what mobo to buy to go with AMD. If you go Intel (P4 3.2GHz w/800 MHz FSB) then you should just get a good Centerwood mobo (Asus, et al)
3) Yes and No. Yes, is does make a difference... but no, not always. There are some instances (such as graphics) where HT is actually worse than non-HT. And many apps (such as audio apps) haven't been tuned to make full (or any) use of it. So yeah... if you get HT, it will impact some things you do, but not all, and in some instances, it may be a performance degredation. And sometimes, you just plain can't use it... i.e. If you run ProTools, digidesign actually mandates that you should disable HT. Basically, it's a case-by-case basis. Once you know which case you are, you'll know if HT is good for you.
4) Check out websites like Aandtech.com and TomsHardware.com for info/reviews on the latest components (mobos, video cards, CPU's etc) and check out places like Sharkyforums.com for a place to ask people about experiences with certain chipsets, CPU's, mobo's, whatever.
WATYF