The s9 really is the most power efficient hardware you can get your hands on right now. Like any investment I'd urge you to weigh the pros vs the potential risks of course, but bitcoin's future does look to be a bright one.
If you decide to go with the s9 their increasingly hard to get your hands on but our website still has a few left. You can also check out our lower cost investments.
http://www.dragonmining.net/https://www.facebook.com/dragonminingworldwideGood Luck!
-Dragon Mining