Someone should try to put aosp's Dsp Manager to work on Froyo Roms!
aosp is based on 2.3.4 Gingerbread.
Gingerbread has an entire framework for managing audio effects. any app can utilize those tools available since its built into gingerbread.
froyo lacks this. the Galaxy S phones had a DSP tool but it was integrated to their touchwiz music player.
basically, even if you find an app that will do this on froyo, its not built INTO froyo and will just run on top of whatever app is playing audio. meaning worse battery life and another process running in the background.
basically, 2.3 is an improvement over 2.2. and the next version will be better then 2.3, if you like the new features, just keep using the new OS. or learn to deal without those features until the small bugs are fixed in the CM7 rom