You folks seem to have a bit of a misconception about replaygain. I suggest you read about it.
It's a good thing, it doesn't normalize the sound of files in order that all quiet parts sound the same loudness as the loud parts, it makes the average percieved loudness the same as the other files in your collection.
For example the replaygain tag on the mp3 file I've got playing right now (Nivarna, Lithium) is -4.70 dB, meaning that when the player comes to play it it will make the song 4.7db quieter.
However, a track of NIN's Ghosts I-IV has a replaygain value of -4.10 dB, making the song 4.7db quieter than it's actual recording volume when played.
This allows all the songs in the collection to sound the same volume, a good thing, as you don't want to be constantly adjusting the volume of your system.
Replaygain does not, I repeat does not, negatively impact sound quality, unless for some reason you like your collection having dramatically different volumes (NOT the same as dynamic range, or "the loudness wars" that people bat on about)
http://en.wikipedia.org/wiki/Replay_Gain read here if you don't believe me.
Otherwise your settings are generally sound, I'd keep "allow 24-bit on" as I have some 24-Bit FLAC files, and I'd just turn EQ off completely. I've no idea how EQ works in winamp so that may be what that setting allows.
