Should put you a little over 400, but in that budget, you've got a budget quad, a 4850, so reasonably good video. If you want to spend more there, look at a 4870 or maybe the new 5xxx series. And a 22 inch monitor. I can vouch for hanns g as I've got one of their 22 inchers myself and I like it. It's been decent for nearly the past year.
But don't think you'll fit much more into 400 bucks. Also, I know the 620 is a weaker quad, but if you can overclock it a bit, it may be a budget beast. You may want to spend a little more and spring for a 720 black edition with unlocked multiplier, but you did specify a quad. On the AM3, don't know that the ddr3 gives a big performance advantage, but with an AM3 board you may be a little more future proof, so if you would like to drop in a faster quad later on, you might be more likely to be able to do that down the road.
May check out newegg.ca and tigerdirect.ca. They should have some similar combos, however there may be a price difference with you being from Canada and all, but definitely some deals to be had certainly.