How to detect an encoded file?

I've been noticing the wide variety of bitrates on Limewire, and I downloaded a 320 kbps song, only to find out out its quality was on par with the 96 kbps version of that song. I don't really have time to go through and test each and every song I download, so I'm wondering, is there a fast and efficient way to detect these files? Obviously people don't understand reencoding to a higher different bitrate does not improve the song's quality. I'm sorry if I'm a bit of a complainer here, but do I have to test every song I download?

Yes. I'm afraid so. Everyone can connect to the Gnutella Network incl. the people that have no idea what they are doing.