I have the same question.

http://www.troyslandscapesupply.com/BulkMaterial.html

Not sure if these topsoil is sufficient or not?

You know, I wonder about this too. I have spread blood meal all over my soil before planting everything and use a transplant fertilizer.

Still not sure if my garden is getting enough of the NPK needed for optimatal vegetation.

Horse manure is the best fertilizer for vegetables full stop. Any aged animal manure is good but horse, rabbit, and sheep are best, with chicken and pig both needing aging and composting well before use.

Green manures - where you plant, allow to grow and til in are also great, but they take time and have to be planned for.

Rotted mouldy hay or straw, and of course compost are also great.

I really enjoyed the books by Eliot Coleman, lots of info on using green manures etc.

-Rosalinda

For growing in pots or to add extra to a veggie garden if you know you didn't get enough compost and manure, I recommend using an organic granular fertilizer like GardenTone by Epsoma. Some of the big nurseries like Menne's have large bags which make it more economical since you can save it for future use. There are other organic brands out there too.
Remy