Apologies to the Gods of Circuitry. Let me rephrase: I will upgrade my hard drive after I get the system, since that is first and foremost. What line of work are you in, Nem?
Cancel the burning then. We never burn the repentent. Well hardly ever.
Many people seem to have a hard time discerning the difference between hard drives and memory. They use the same terminology so they must be the same right? Good to see that you have already advanced beyond that stage. It will make it easier on Will.
Computers aren't my work, they are just a hobby for me. But I have built and rebuilt my own, including a dual CPU model. I also at times get called in to help by the IT people at work and co-workers who can't get the IT people to help. Not to mention called for help by friends including one who builds, sells and supports computers for a living. It can be really fun to see the looks on their face when I pull answers out of my hat to problems that have plagued them for hours or days.
You said that you are considering collecting the parts and building one yourself. If you do so I would recomend collecting the parts that change least first.
Case, powersupply (abbreviated as PSU commonly- get a good one) , keyboard, mouse. All are pretty standardized and don't change a great deal and can be bought early. There are cases now where HDs, CD-Roms and Floppys can be inserted and removed without tools. Highly recommended. Right now one of my machines has an improperly mounted DVD because I couldn't find the box with the custom drive rails, I have now and will fix it over Christmas, a better case would have avoided that problem.
CPUs, motherboards and memory change quicker and paying a high price for something that won't be used until it would have been half the price isn't practical.
It also helps if you have kept parts from your old machines that you can scavenge for parts while delaying some purchases. For example an old video card will let you know that your motherboard, CPU and RAM are working before you have the budget to buy the good card and before your stores return date runs by. Same for old HD and CD-Roms. Salvaging floppy drives is also a lifesaver at times.
Above all is one thing -
RESEARCH is your friend. By reading online reviews and problems other people have had you can avoid many of the lemons and stay with the caviar and champagne. Use of quality components will help your systems stability and reliablity immensely.
Also I suggest a UPS (uninterruptible power supply) with brownout protection. Such a unit will also save you hassles. 85% of all computer problems are power not software or other hardware. The UPS will help you avoid problems with low power. Tripplite and APC seem to be good. Which is also why I said earlier to get a good PSU not a cheap one, I use Antec and Enermax.