If you cannot sustain a low KH (acidic) enviornment (<4-6dKH), you should not get Aquasoil. Aquasoil is by far my favorite substrate, but if I had to use it with hard tap water, I wouldn't see much difference between it or anything else. I would likely go with EC. AS is a 'specialist' substrate, used for particular reasons, primarily growing soft water plants. I think the benefits of using a soil-based substrate are a little greater overall.
I've noticed Power Sand being a controversial subject. I'll tell you this: it's a circumstantial addition. It's sole purpose is to jump-start plants in the early stage of growth. Its effects will wear off. Does it work? Absolutely--for what it's intended to do--there's a short time frame in which it works extremely well. It's not something to be measured over the long term because it doesn't influence the long term directly. I want you to keep in mind that AS and PS are planted tank substrates. Fish come after the fact. If you want to complain about ammonia levels, use another substrate. Is AS worth the price? Yes. If you're not willing to go 'all out' on your planted tank, then no, it's a waste of your money.