I've been with customhydronutrients.com for a while now and couldn't be happier. Inexpensive dry salts, organics, and amendments... and shipping isn't too bad either.
Full articulation of feed is a huge bonus when fixing problems or meeting specific feeding needs.
Use something like hydrobuddy if you're wanting to dial it in for each fertilizer, or do like I did and just experiment to see what works. Its a lot of work but i'm glad I did it; I do NOT miss buying expensive bottles of water!