Personally, I would find a local, reputable, and independent computer store and talk to them. Chances are they'll get the parts at a good price and put it together for an extra $40. You'll get what you want, and if there are any hassles or questions it's WAY easier to deal with than ordering online.
If you have the cash, places like VooDoo (which is 4 blocks away from me), Falcon Northwest, and Alienware put together some fantastic machines and support won't be an issue. Unfortunately, that level of support costs extra dollars, but then again you get what you pay for. I would be wary of many of the smaller online outfits...procede with caution.
For a good, all-round machine (complete with a monitor) that will handle games and multimedia, expect to pay around $1500~$2000 Canadian. Best bang-for-the-buck is the smart way to go, IMHO.
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