Have you tried the Canadian Forums? They would probably be of help to you in your search.

Any top soil will have weed seeds, they were in the soil before it was removed from whatever land it was on, they blow in while the top soil is stored at the supply yard and they blow in to your yard after the top soil is raked out. You may be able to buy bagged soil that has been heated to kill weed seeds, but it would be very, very, very expensive to buy 57 cubic yards in bags.

To control weeds in newly installed top soil, cover it with 4" to 6" of mulch. You can hand pull any weeds that poke through or you can use Round up on them.

Thank you for the advice. So how to define good quality top soil? I am really new in gardening. I need all the advice I could get.

I would define good quality top soil as loam with with a balance between organic content and drainage. There are simple at home tests you can do to test soil.

The link below contains lots of information. Go the soil anaylsis button and then the composition button for descriptions of how to test soil at home.

Here is a link that might be useful: Soil