No experience personally.
Let's see...$40-$80 RAM, $100-$150 CPU, $80-$120 motherboard, leaves...$150-$280 for a video card. Didn't count shipping, but still.
Ah, Canada. Hrm...
I'm looking up parts here, but you've confused me. Your profile says you're in Canada, yet you've specified USD as your budget. While this is helpful in that it gives me somewhere to estimate (read above), it seems to imply to me that you're buying from a US re/e-tailer. So if it's not a straight conversion, a CAD budget would be more helpful-for instance, if you're buying in Canada. (xe.com/ucc says 616, is that about right?)
When you say barebone, you also imply to me that you're going to need a case and a power supply, as your old PSU obviously isn't going to work. Is there any particular reason you'd apparently prefer to do a barebone and add a CPU and video card rather than building from parts?
Also, 4GB of RAM or 2GB?
And, finally, which is more important to you, CPU or GPU? I'd assume CPU but just making sure-it's a personal preference, obviously. For instance, would you prefer a dual core system with a 4850, or a quad core system with a 3870? (I'm partial to ATI at the moment, as the only real place Nvidia beats them right now is the >$300 range, which most of us simply can't afford.)
The above is just examples, though-I'm currently itemizing out a build for an E5200/3870 system, as I'm almost certain that configuration, at least, will be under budget.