Depends on your operating system as well...Considernig X-Fi cards need to run Alchemy in order to get audio to work in directsound related games in vista.

If you are windows based...The Auzentech X-Fi Prelude is a godly card at it's price of 170 atm.

http://www.newegg.com/Product/Product.aspx?Item=N82E16829156005&Tpk=x-fi%2bprelude 

A higher quality card compared to the X-Fi platinum fatality...But you just don't get the front 5.25 audio connections and remote. Damn still worth it though....The lower end X-Fi's are also good..But don't go wayyyy too low..I can't recall which X-fi cards do this, but their lowest end x-fi's aren't even x-fi's...they are audigies with X-fi software emulation...Just make sure you don't go too low. The other X-fi cards are goodies ^_^.  The Asus Xonar is alrso a fantastic card, but costs a bit more...A good card for vista...Although I'd still nab a X-Fi platinum since Windows xp is my OS of choice ^_^.

 is the price on the auzentech likely to go down within next 3-6 months ?

 i heard asus makes some pretty good sound cards though i havent seen them anywhere but then again i havent looked

auzentech hands down.  Kamrooz posted a review recently with auzentech and asus being compared with one another.

I just ordered the Auzentech X-Fi for myself =D...I just pretty much maxed out my credit card on a new keyboard, mouse, headset, and x-fi prelude >_<. But I had to celebrate for this new skulltrail rig! =D..::bows to hothardware::

Back to the ops question...Here are 2 reviews comparing the Auzentech X-Fi Prelude and the Asus xonair...The two cards you should be looking at if you have a lax budget =D..

http://www.extremetech.com/article2/0,1697,2268255,00.asp 

http://www.driverheaven.net/reviews/preludeandxonarsoundcards/index.php

Make sure you read both. It's always a good idea to read several reviews to get the full scope on the product ^_^. 

Actually..The onboard memory is in use, same for the x-fi prelude as well =P...It gives you a slight FPS increase too ^_^...very small though =P. 

if you have the money,auzentech is the way to go!Also,EAX 5.0 is also supported by the ASUS audio card,which is cheaper

X-Fi Xtrememusic by far.

The Prelude is nice, but expensive, and the XRAM isn't really used / even useful. $180 vs $70, for nearly the same thing. 

The Xtrememusic was expensive when released, so they slimed it down, removed a few things and made the Xtremegamer. Since then it has gotten much cheaper than the Gamer.