If you only need output for your headphones then this Fiio E10 is a very good deal right now. If you also need RCA outputs for speakers then NuForce UDAC2 is a descent alternative.
http://www.newegg.com/Product/Product.aspx?Item=N82E16829102032 also it has phono in, line out and a ground screw optical in and out and usb in suports 24bit @96k
The Fiio e17 is an excelent choice. I love mine paired with my Philips Citiscape Uptown.. I've also tried it with my buddie's m50s, and it sounds great.
the Fiio e17has a signal to noise ration of 109db and the sound blaster x-fi hd s/n is 114db every 3db is a and noise doubling in quality
I don't know what you tried to say with this sentence but the S/N ratio is irrelevant in this case. I'm pretty sure the E17 has a better D/A conversion circuit, and the X-Fi lacks an amplifier anyways. I've had a Creative USB soundcard, and while it's okay for the price I would never get it over a Fiio for headphones. Here's a post about a user who upgraded his X-Fi card to an E17 over at Head-fi:
Hi Uchikoma,
I just want to add my opinion on your situation since it sounds very familiar to what i went through a while ago.
I had the exact same sound card and in my 'comfortable' world of computers I was always a 'soundcard' guy specifically 'Creative' cause I liked their sound.
When I took a chance on the E17 I was immediately rewarded and all fears quickly vanished!
The E17 was a vast improvement to my Xtreme Music in ways like:
Driver less, plug and play! Not having to install a billion crappy software programs was liberating! (As a computer guy, I am deadly serious about this point!)
Sound quality and clarity is simply 'High End' to my ears, you get a big 'Wow' factor going from a sound card to a 'proper' Dac/Amp.
Functionality is simple and user friendly. I can adjust volume/treb/bass etc. off the E17. Power it on and off and sits comfortable on my desktop next to my rig.
I was afraid it wouldn't preform well in games like BF3, Css, Diablo 3 or many of my other steam games but guess what...not a single issue/error/glitch. Sound is fantastic and I was not disappointed at all! I've played many rounds of CSS with the E17/AD700 and I can still track movement very easily! Before the E17 I was using the Xtreme Music with BF3 and when i switched over I could not hear any lack of detail compared to the creative card!
I just want to go back to your original question in regards to if the dac on the E17 better than the Xtreme Music, well in my opinion I believe it is! I use to have to tweak the settings like crystaliser and that just to make the sound good but with the E17 I did not have to adjust anything I loved the sound it's powerful, impactful and crystal clear! (If you've used a creative card then you know about the so called 'enhancements' creative implement in to the drivers just to make it sound decent.
Also you asked about the Asus equivalents, all I can say is before the Xtreme Music I had the Asus Xonar D1 for a short while but I did not like the sound at all and 'enjoyed' the Creative sound better!
Well I hope that helps a bit Uchi, just giving you my experience going from the Creative XFI Xtreme Music to the Fiio E7.
(P.s I'll be using the E17 until the wheels fall off LOL!)
and @ spittis Sound Energy Doubles Every 3 dB. Example: if a 90 dB noise is doubled, it measures 93 dB. and inorder to have the higher s/n you have to have better parts or the sound distortion happens. But, it seems like the e17 is a better choise for Box Ov Rocks because he can use it with his tablet. also i wasn't saying that the sound blaster was drasticly better than the e17 just that from the specs the sound blaster has a slight lead. I was also, pointing out the features of the sound blaster.
The Creative Sound Blaster X-Fi HD has a headphone amp "High quality headphone amp supports studio-quality headphones (e.g. <=330Ohms)."(taken off the website) and all a amp dose is makes the sound louder. to top it off the Audio Technica ATH M5 headphones are only 38 ohms so this audio card can more than support them.
There is something to be said about personal opinion how the divice colors the audio and if the device is neutral, base heavy or treble heavy. and sence i have not owned this product i cant say it s good or bad using this criteria. but i can say that the sound blaster fatality dose well with high res 24bit @192 files. it is very neutral but you can fine tune how you want the sound to be. ie base or treble. I am now using a xonar essence st because i needed some thing better to record records with. and I love this thing.
@Akira4950 Allright cheers for a better post, the first one just sounded so messy, I know how the logarithmic sound scale works :) The S/N ratio is still kinda unreliable though since it depends on at what power it has been measured, so to really be able to conclude that X is better than Y regarding the SNR it should say "103 dB at 1 Watt" just as an example.
My bad on the amplifier, out of my head I didn't remember that the X-Fi has one. It's true that low impedance headphones generally don't need an amp, and you should definitely not spend money on a separate amplifier for something like the ATH-M50. But getting something like the Fiio E17 is a quite good investment IMO, since it can power more difficult headphones too meaning he is set for the future if ever wanting o upgrade headphones.