I imported an amplifier, not a pair of speakers. Obviously, from a perspective of size, weight, etc., it would be much easier than what you will be faced with.
Still, the brokerage fees and duties were applicable. For audio electronics, the tariff is 4.9%, though speakers may be on a different rate, which you can look up via the link generously provided by Zeneith. I hear that speakers shipped as "cabinets", and having no drivers mounted and things like that come in as "furniture", and the tariff on that is supposedly negligible. In your case, as with most people, it is not applicable, unfortunately.
My transaction was handled by FedEX, and I must say I was more than happy with their service. I provided my SSN to the seller, along with the extra funds related to the tariffs. They handled getting it through Customs. The package was being delivered from the Toronto area to me, just outside of Philadelphia. It was shipped at about 6:30 PM Wednesday night, and was on my doorstep before 10 AM Friday.
A couple weeks later, FedEX sent me a bill for their brokerage fees. The rates were provided to me prior to shipment; I considered them reasonable enough to go through with the whole thing. Unlike some of the horror stories, there were no surprises regarding the brokerage fees and the like down the road.
I was luckier than many I read about here. All in all, it was a superlative transaction. I would say that the most important thing is to do your homework prior to committing to anything, make sure you have all of the information up front, and finally, having a partner just as diligent as you on the other side of the deal can be the difference between things going right or not.