Bittrex and Poloniex are the only two exchanges that I use and trust but I prefer Bittrex simply because of their speed in responding to inquiries and fixing problems.
I think the answer to this question would depend heavily on how much your other investments are total. If your other investments are big, and $3,000 is relatively small, then I would suggest gambling a bit on smaller coins. If not, your current portfolio of 5 coins is already pretty diverse so maybe spread it around the 5 of them.
It's interesting that you bring this up. I have made a small investment in this coin as well looking at its potential after the new developers create something unique.
10 times "soon" might be dependent on what your definition of soon is. However, because it's such a small market cap coin with top holders accounting for most of the coins (meaning there would be a shortage of trading supply), and less than 2 million coins currently, I think 5x+ within a month does not look impossible.