Yeah, I don't know if you really need the Quad core processor, only if you want to have absolutely the fastest thing on the market. The E6600 is a great processor, and is only 300 USD as opposed to 1200 USD for that processor. Also, note that the quad core processor isn't going to see much of an advantage in gaming for a little while until developers start to fully utilize multiple cores.
Anyway, you should really get a more powerful PSU. 450 watts is just not going to cut it with this PC. I would look at at least 500 and preferably a 600 watt power supply by a quality brand like Antec.
Something else to think about is where you're going to buy the parts from. If you buy it from a reputable online retailer like Newegg, you can save a lot of money. For example. that graphics card is only ~$725 CAD on Newegg as opposed to $850