I installed amaroK without xine and then later found out its essential for efficient mp3s. So I installed xine and looked for it in the "Chose Engine" section but it didn't show up. So I went to their webpage and found out I have to re-build amaroK. So I download the source tar and try a ./config. I end up getting this error:

checking for Qt... configure: error: Qt (>= Qt 3.3 and < 4.0) (headers and libraries) not found. Please check your installation!
For more details about this problem, look at the end of config.log.

is it possible to just re-install the rpm or do I have to build from the tar. If so, how do I fix this error?

You need to install the qt developemnt libraries. Since you didn't mention what distro you are using, I can't offer any specific tips on how to install them.