I know you're looking at upgrading the older board, but have you considered just minor upgrades to your beefier box?

Specifically add another 4 GB to your main board and move to a 64 bit OS if you are not already on one?

You can run Windows 7 RC1 in 64 bit for free for almost a year at this time, and I'm guessing your mobo can handle 8 GB if it can run a quad core.

As far as upgrading your secondary box, you're likely to get caught in an upgrade cascade.

You need a burlier processor, which necessitates a new mobo, and while you're at it more memory is cheap, then graphics card. Oops PSU upgrade perhaps as well.

Anandtech does regular buyer's guides for gaming computers in different budget segments, I've often found them a great resource when doing builds.

You're an Intel guy, so here
http://www.anandtech.com/guides/showdoc.aspx?i=3563&p=3

That's the Entry level build, they have a budget build as well, and an enthusiast level, including AMD options.

I think Newegg has plenty of capability for Canadian folks. Some great options and you can get well under those budgets by reusing parts.