Wow, that was an interesting 4 pages lol!
Dave, bottom line is this:
You went to an lfs, bought two fish, put them in your tank, your tank spiked ammonia, the fish died.
I've bought corals before where I didn't know much on, but I knew the family they were in, and the general requirements.
Now with fish, here's what I do: Excuse me, what kind of fish is that, it's really cool. Oh that's a so and so fish. Ah thanks. I then pull out my phone, google the name of the fish, find it, then read up on it and decide if it would be a good fit for my tank. Takes literally a couple minutes to find the fish, then a couple more to read up on it. There is such a thing as an impulse buy, but with having the capability of googling the fish to learn about before you buy it, it's not so much a RISKY impulse buy.
You've asked everyone a question, you were given excellent answers. Ammonia, need established systems, etc. For some reason you are not seeing the forest for the trees. You're taking everyone's posts as personal attacks, something you do all the time, then turn the tables and say, well like none of you have done the same thing. That makes no sense whatsoever.
If I had a fish die because of something I overlooked and it was pointed out by someone, my reaction would be something like this: Oh, dang it, I didn't even think of that. There is nothing wrong with making mistakes. This isn't the easiest of hobby's, and I consider it the pinnacle of aquarium keeping, which is why it makes no sense to get butthurt when people give you advice.
My suggestion, take it or leave it is this, if you don't already have tests kits, buy some. Test your own water vs. bringing to an lfs. Next time you buy a fish, pull out your phone and google what you're intending on getting.
As Joe mentioned, if you're still unsure about a certain fish, put a deposit on the fish, go home and do some research on it. There isn't any harm in doing that.