Hi mate,
Well it's up to you how you spend your money. As far as I'm concerned, the most important box to tick is the one labeled "I am not a sucker". Dosing EI mans never having to worry about sediment fertilization, and if you did want to cover that base, because it doesn't hurt, then one could easily use Osmocote lining the bottom of the tank, which is about as cheap as it's ever going to get. Heck, you could simply line the bottom of the tank with NPK + trace powders or soak Akadama in a rich solution as demonstrated by JamesC.
It's much more important to understand WHY you failed and WHY you succeeded. To understand the mechanics of your components is the best guarantee of future success. Powersand's super high concentration of NPK is used because that system does not dose the water column for weeks, and when that system does call for water column dosing, the concentrations are relatively low, so the sediment has to be enriched significantly, otherwise the plants risk suffering nutrient deficiency. But you are dosing the water column so spending megabucks on pumice is not the wisest bang-for-buck.
Cheers,