Someone mentioned applying a limiter to your tracks... interesting idea for transient peaks, but most 'radio-friendly' music is squashed and over-compressed anyway, so you run the risk of completely ruining the dynamic range of your source material.
In fact, the Crystalizer (which I have set on 50 percent) is designed to reincorporate crisp, transient and percussive sounds back into the mix to give a more lively, energetic and clear audio experience.
For my 5.1 surround speakers, I have them set to CMSS-3D Surround 'Stereo Surround' rather than 'Stereo Xpand'. Stereo surround just duplicates the front two channels in your rear ones, which for me gives the best sounding music.
My speakers also sound great with the EQ set to 'EQ Rock'.
I'm using a Logitech Z-5450 speaker setup with the X-Fi platinum, and a pair of Sennheisser HD-477 headphones in reserve.
As for the opinion that Creative stuff is no good for critical listening or in other respects, I suggest you read up on some comparisons of the X-Fi vs M-Audio's consumer-level sound hardware because the results will surprise you - the SNR and frequency response of the Creative hardware is better and more faithful respectively.
I'm qualified in Music Technology and I love the versatility that the X-Fi gives for all tasks from music creation to audio playback to gaming. Unless you have really specific audio recording requirements I would find it very hard to be swayed by the Audiophile 24/192, especially because it has none of the advanced DSP capabilities that creative implement.
As for studio monitors, yes they sound 'faithful' but that doesn't necessarily mean 'better'. Monitors are designed to clearly portray an audio signal - warts and all. However, it is widely known that most home audio gear 'colors' the sound to varying degrees. This may actually mean that the resulting sound is more pleasing to the ear than the average monitors which can sometimes sound a little hollow unless you spend alot of money. Home audio speakers are also designed to have a wider sound field than studio monitors, which are designed to be more precise. Sometimes its better to compare apples to apples, I don't think studio monitors are the right way to go for most people. Of course for mixing, but not neccessarily for general use.
Oh, and if you like to 'enhance' your MP3's then get the Izotope Ozone plugin for Winamp. I've been using it since long before I ever purchased an X-Fi and you will NOT be dissappointed.
X-Fi + Logitech Z-5450 + EQ + Crystaliser + Stereo Surround +
Ozone (Valve EQ + Room Modelling + Bass Compression + Tube Limiter + Tube Saturation)
= VERY happy ears.
Oh, but I'd recommend leaving things plain for gaming. You will certainly regret using the Crystalizer with gunfire.