I personally use Amquel, and I've used it since I got into the hobby. Very reliable. You could combine it with Novaqua (both by Kordon) and these two will get rid of all the unsafe chemicals and metals in your water.
Prime is much more concentrated than Amquel/Amquel Plus. So while the bottle may be more expensive, it is cheaper because you use significantly less of it.
Anyone using Amquel should seriously consider switching to Prime. It has saved me mucho $$$$.