OK here is the truth as I understand it but I am a xonar fan so take from it what you will. My sound card history is
SB Live 5.1 > Audigy 2 > X-Fi gamer > Xonar DX , Xonar Essence STX
EAX is dead
Unless you are still into playing your old games (nothing wrong with that) then forget about EAX when choosing a new SQ. Most of the old EAX enhancements wont work naively on win 7 and is re written by OpenAL. Stick with XP and EAX for gaming nostalgia on old PCs and games.
The Creative Camp
Its a bit of a sweeping statement but most of the creative cards have been rehashes with gimmicky branding to sell them. They have not really improved the tech \ SQ for a long time until the titanium arrived.
I tried a lower end X-fi and had driver issues up to my ears (no pun) and as a ten year creative user that was the end..
(I still hear good things about the KX driver pack which is the only saving grace of the X-fi)
Xonar ( Dolby Headphone & Pro-logic IIx ) vs CMSS3D
Plenty has been argued over this but IMO Dolby headphone is superior than CMSS3D in sound quality and positional accuracy vertically and horizontally and general audio experience. I find it doesn't distort the SQ as to make the audio experience a horrid one. You also have the option of adding Pro-logic IIx for even more sound stage and imaging customisation.
The lower end Xonars (DG & DX) have Dolby tech including digital live 5.1 encoding for a bargain price. You should be hard pushed to not choose a Xonar when looking low and mid range.
The DX sound quality is much better than the lower end offerings from creative and has full windows 7 64bit drivers with ASIO with which I have no problems. Not to say ASUS are perfect many have had issues and their driver release schedule is iffy, but for that we can use the custom Unified driver pack. Big up to the custom driver mod scene.
Higher End: Essence STX vs Titanium HD
The STX brings a quality DAC and not just a built headphone amp and is well regarded here on head-fi and gives a noticeable bump in SQ over the DX. The HP amp may not be high end audiophile league but it can power some audiophile cans (HD650). The STX is regarded as up there with if not the best sound card available.
I have not heard the Titanium HD but this looks to be a great card from creative and if I was still in the creative camp I would probably buy it. Reading the reviews the sound quality is comparable and for some even better than STX.
Which to buy
For me the Xonars represent the best sound card for gaming and music & movies and the top offering being the STX. Ever since I fist purchased the DX was a very happy Head-fier and Game-fier and now with the STX even more so.
The only creative offering that should be considered is the Titanium HD but without dolby headphone it will be second choice every time.
The X-fi HD / Digital music premium external Sound card looks to be a great external option but lacks flexibility for gaming.