So I've been reading around the forums here for a while and I am a bit confused about the sample rate for MP3's.

It seems all my MP3's are listed as 44.1khz (through winamp). Does this mean they are 16-Bit?

If they are 16-Bit, then what advantage do I gain by using a 24-Bit sound card and a 24-bit input plug-in for Winamp?

It seems 24-bit is supposed to be better, but if the mp3's are encoded at 44.1/16, then how can I realize the benefits?

Thanks.

44.1kHz refers to the sampling rate and has nothing to do with the dynamic range (16 bits).

An MP3 has no instrisic 'bitness' (you could best think of it as being variable), even though the source material may have been only 16 bits. Upon decoding, you can round/truncate it to 64, 32, 24, 16, 8 or whatever bits. The more you use, the less additional loss you have from the rounding. So this is why even though the original material was only 16 bits, there's still benefit in using more on decoding.