To Lake Champlain, coming from the East Coast it's up the Hudson to the Champlain Canal, where you do need to unstep. The Canal takes about 1.5 days, about 5-days in total from NY.
A benefit of buying on Lake Ontario is that they're mostly fresh water boats, of course. Prices are much cheaper on the US side than in Canada. A friend of mine bought a Catalina-30 in Rochester late in the season last year, in fact, for exactly that, $18K.