Pete,
I'm not sure but, does Forward Air go somewhere close to the destination you need it to arrive at? I've had a CAI Raptor shipped from NJ to Seattle and the shipping was fairly reasonable, a hell of a lot less than Fedex or any of the others you mentioned. Any possible way you can squeeze the size of the box a little to get it within Canada posts max dimensions?
How close are you to the US border? I've shipped out quite a few items from the US side as it's only a half mile drive for me but it usually costs me less than half of what shipping from Canada costs.
I recently shipped out a glider that from Canada to Wyoming was going to cost $89cdn, I took it into Sumas Washington and sent it USPS for $8.70.
I also shipped a guitar fedex from Sumas to England and it cost me $220, same shipment from Abbotsford to England (sussex) was $479.
Might be worth looking into.