Check out a local supplier to you; try
http://www.ncix.com
You can get preconfigured systems, or one built with components you specify, or even just get parts from them.
There are various review sites which "build" systems in various price ranges; for instance look at the guides at
AnandTech or the SystemBuilder Guides found at
Tom's Hardware $
500 Gaming PC,
$1,000 Enthusiast PC and
$2,000 Performance PC.
Building a PC is really not rocket science at all; it's a question of ordering the parts you need, and then plugging the various bits together.
Also do remember that some pieces of older PCs can easily be recycled! Monitors / keyboards / mice come to mind, along with printers, other peripherals, even hard drives can be (although I tend to be a pack rat with those and keep old drives).
Even sound cards can for the whole be retained, if you do decide that you want a discrete sound card rather than the one built into the majority of all new motherboards.