Canadian market wise, the best sites to order from are Memory Express and Tiger Direct. I think the states best site to start at is Newegg, but don't quote me.
These guys seem to have you down for parts ideas, but I just want you to know if you build a top-of-the-line yet price-point balanced PC, (Say a core i7 with an X58 MOBO), don't be surprised to run yourself $2000 CDN.
Be careful when picking a case-- you really don't need anything fancy, but if you want something that looks sweet for price point, look at Cooler Mastar cases, and branch out your parts from there.
Now, I'm not a huge gear head, but I've done quite a few builds by now. What this thread looks like so far is tricky to pinpoint... So I'll give you little procedural guide, if'n perhaps that's the way you think.
1. Pick your case. Take note of how much space you have for it and all that jazz, and the proportions of the inside. You'll need to make sure you've got enough room for all your parts.
2. Motherboard. I'm sure other gear-heads say what's good here, but this is the part you should start picking right after your case, because it will determine a lot of the compatability of your other parts.
3. Processor - This concerns your power for processing. Now, I may be a little biased, but last I checked, the Intel i7, Bloomfield 950 is super-overclockable, and the cheapest core i7 on the market right now. I'm not an AMD fangirl, so I can't really speak to the competition's product.
4. EVERYTHING ELSE. From here, just fiddle to see how much power you can cram in for your budget. For gaming, focus on your RAM and Video Card(s). You can probably bolster your budget a little if you find good deals on parts bundles for the above parts on said websites.
Saving on shipping is another way to weedle more bang for your buck.
And if'n you like what I have to say, I'll check back and keep helpin' you out mate. Support on these kinds of projects, especially the first time, is crucial.
