my brother-in-law is a systems administrator, and i was fortunate enough to hook him up with a job at a good animation company, which further maxed out his skill level and applicable knowledge.
so my point here is that: he is a "collector" of computer parts and knows how to build one from scratch, and for the money you have, you need either to learn this knowledge, or you need to get an internship at a local production company where you can find people to learn from as i've done. I cannot build a computer, but i learned how to ask the right questions by learning how to follow directions from people who do.
a good place to buy stuff from is http://outpost.com/ which is Fryes in LA, CA, USA. they have a lot of good sales. also a good site to check prices at is pricewatch.com and general stuff you can goto froogle.com
also consider that you might use a cheaper computer for building your project, the basic stuff, and then when you save the money while building the project and getting info on a better computer than you have, buy a better one for rendering and compositing the project.
the other option is to get a lean, basic computer with a great motherboard, decent enough graphics card, an external harddrive for backup, a smaller wacom [9 x 12 is very doable] and you can buy an old fashioned monitor even at a salvation army store for $25 nowadays, 21". Do ONLY the basics, what you absolutely need for hardware and software, and then save any money to soup up your system with a better graphics card and sound card when you're ready to do the heavier lifting. Just getting a project planned and started properly takes a long enough time so that this is a doable plan.
and get that internship at a local production company or TV/media station, local university, etc.