This is my first grow back after awhile off, but I used to use Peters Bloom Booster. You have to get it online these days though. They used to sell it at Lowe's, Home Depot, etc. Apparently Peters bought the brand back from Scott's/Miracle Gro. I noticed that the Miracle Gro Bloom Booster that they still sell in stores is pretty much the same thing just in powder form. I plan to use that.
I think all those high priced ferts are a huge waste of money. Granted I've never used them, but I can't complain about the results I got from the "cheap" stuff.