You can probably order even if your not canadian... not sure.
The Logitech 5.1 X-540 system is on sale at NCIX and with all rebates will go for 29.98. I personnally got the same system but paid more than this for.
As I did, you can just use the sub and the 2 front speakers for your cab. I chose that set because of the handy remote that comes with it. There is a knob for master volume and a separate one for bass. There is also a button on the remote that is supposed to simulate surround sound with only 2 speakers plugged in. They are worth it just for the remote but the speakers and sub do sound pretty good.
Good choice if your in search for your cab speakers.
One downside: if you plan to leave the remote on the very top of your machine, the wire could be too short to the sub so either you put the remote elsewhere, fix the sub higher in the cab or re-wire the remote.