In comparing the onboard sound with this creative x-fi card it was pretty clear there was a noticeable improvement of clarity with the x-fi, using the 'creative enhancements' in the software drivers had the complete opposite effect though. Particularly the crystalizer, which just made things sound shrill and and metallic, maybe on poor quality speakers it would give some extra 'sparkle' to the music but on good speakers the extra processing just destroys the artists intentions and well, ruins the sound quality.
The main reason I got this card was so that I could send a digital audio signal via optical spdif to my av amp, it has performed great at this and compatibility is great.
The x-fi series is focussed on gaming, and although i'm not a hardcore gamer it does help to improve the spatial positioning of sounds, making is more immersive in a game like battlefield. Also having a dedicated soundcard can give you a slight FPS increase as it takes some of the sound processing away from the main cpu.
To be honest i'm not sure i'd buy another one, they're quite cheap but for my uses (mainly home cinema) I think a motherboard with HDMI out would be perfect for my needs, I can probably live with the slightly worse sound quality in games.
I managed to pick up an OEM Version of the Creative Sound Blaster X-Fi Xtreme Music from eBay for around £30 around 3 months ago.
It is very easy to install, simply slot it into an empty slot and install the drivers and software.
Wow! What a difference!
I upgraded from onboard sound and the quality difference is unbelievable. I have the card paired with Logitech z-640 5.1 Surround Sound Speakers and a Medusa Speedlink 5.1 Surround headset.
Not only does the card come packed with features for example the 24-bit crystaliser, but it is easy to use and configure with the Creative Audio Console.
The card make sounds in games beautiful and music is perfect.
I had a lot of teething problem with the card. At first, whenever I reset my PC, the card settings were defaulted to headphones, when my speakers were plugged in, muting my speakers. This problem eventualy went away however.
Another problem I have is when I switch modes (Game mode -> Entertainment Mode) there is a horrible crackling sound made by the card. Sadly, this is a problem that many people have, as I have seen numerous threads on the Creative forums.
Although there are evident problems with the card, I still wouldn't go back on my decision to purchase it. In game mode, music still sounds much better than onboard sound. I still give the card 4 Stars, and would recommend buying one.