+1 on dry ferts you mix yourself as the best option. Cheap, easy once you get your head wrapped around dosages and easy to adjust for the needs of your actual tank. There's a number of places that sell a fairly standard pre-mix of dry fert macro/micro's if you want it even simpler.
For premixed liquid, I've been very happy with Pfertz's macro, micro and potassium (my tank's a potassium hog-your's may not be) and their root tabs are pretty much equivalent to seachem's. I've only moved away from Pfertz due to the cost and need to fine-tune the mix as I've moved several of my tanks up to moderate lighting and added a variety of more demanding plants.