If you're talking about the spectrometer that input plugins send data to be shown in the skin... it isn't accurate at all for telling what level something is.
If you want a good spectrograph plus PPM & rms metering, as a Winamp dsp... check out DSP Spectrum Tool.
http://spectool.megafongsm.net/If you want just meters, there's this:
http://www.winamp.com/plugins/details/11489but i can't vouch for weather the metering is good or not. It looks like it only is a PPM, but impossible to tell without using it. Try it.

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ok, i tried "Peak", it's a piece of crap if you want to use it for detecting if the audio is going over -0dbfs, because it doesn't show it. lol. Try the DSP Spectrum Tool demo.
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