Yes, or alternately, you can just rename your current minecraft.jar file to minecraft1.0, and place the 1.8 jar in there, named minecraft.jar.
There is no 1.9 if you open minecraft the log in and click update then you will get the most up to date minecraft 1.0.0. But if you do you cannot then come on the server as it will say outdated.
Jordan, look around the forums here. Pythros has a 1.81 jar, which is what you need to play on the server.