I've owned a bunch of different low cost digital recorders over the past 8 years. My least favorite was the original Zoom H4. ( terrible preamps, terrible sound ) I know that the Zoom H4n is a big improvement, but I am still not crazy about the mics or the preamps. My favorite recorder for overall sound ( especially the built-in mics ) is the Sony PCM-D50, which I sold and will probably end up buying it again. Right now I'm mostly using an Olympus LS-11 which comes close to the sound of the Sony PCM-D50, but the mics are just not as good. Try listening to the Texas Media Systems mic test to see how much better the Sony PCM-D50 mics sound compared to the Zoom H4n...
Texas Media Systems Stereo Mic Test
Texas Media Systems Stereo Mic Test