As long as they ship USPS , the US Postal Service, and NOT Fedex, UPS, and the like your brokerage fees will only ever be $5.
The Courier companies gouge you big time on brokerage, as you found out with your Swiss chocolatets. And they will tell you it's because they have to fill out forms, etc, except that it's the shipper that fills out the forms, not them! Complete rip-off in my opinion and I will never use them for that reason.
Most times, Canada post won't even charge you duty or GST on items coming in. It's really a crap shoot whether they do or not, as they just pull random items coming in for duty and GST and not everything gets processed for duty and GST. Must be their paperwork saving program!
Understand, though, that the higher the value of your items, the more likely they WILL bother with the paperwork as the GST you would owe would make it worth it.
As for what you pay for duty, it all depends on whether your items are dutiable. You can check for sure at the Canada Customs website. Just google it and it will come up.
My experience has been that CD's are not dutiable, but don't quote me on that as I could be wrong. Just check the website.
...there's also something about if it's made in the US or not (whatever that means), etc etc.