Basically I don't want the hassle of collecting my bags, going through immigration and having to check in again for the last leg of the journey.
That is
exactly what you will have to do. You go through BCP (Immigration and Customs) when you first land in the US, collect your bags, carry them through Customs, then recheck them. They usually have a recheck desk within the Customs area, right after you clear Customs.
It is actually rather painless. I've done it dozens of times.
I have never been to Toronto, but have heard you can clear US Immigration and Customs before your US-bound flight. Others can give you exact information.