Looking to get better sound out of my PC

Right now I have an X-Fi Titanium (Not the HD version), and I'm trying to decide how to go about getting better sound.  It's my understanding that this card's weakness is primarily it's lower quality op amps, correct?  

I could modify it, but I'm under the impression that using the front panel audio connector on my case isn't the best option and I'm not too thrilled with having top plug into the back constantly.  

So what i'm looking at getting is either an external DAC + amp (whether discrete or in one unit) or maybe getting a Titanium HD and then using it to get a clean line out to an amp.  Does this card have HD audio front panel connectors?  Admittedly I probably wouldn't use them but I hate having "dead" connectors on my computer.  

On one hand, getting the analog stage entirely out of my computer would probably cut down on interference, but on the other hand, running an external DAC off optical could make things more complicated, especially if I just want to switch to my speakers.  

Right now I have a pair of ATH-A900 but I'm looking at getting a pair of either Beyer DT 880's or Senn HD 598's.  Any ideas on good options for this?  I'd like to try and keep the overall price (sans phones) to about $250.  

Does anyone know if an X-Fi's audio manipulation options such as its HRTF (CMSS) still work if its outputting over optical?  

Thanks for the recommendations, I looked at the HRT but I don't think it's what I'm looking for.  That is, assuming that what I'm looking for would actually work as intended.  What I'm looking to do is hook this DAC up to my X-Fi over optical, the idea being to preserve my X-Fi's HRTF functions so I don't have to fool around with cables to switch from a normal to a gaming optimized set up, plus I could use the same headphones as well.  If I use one audio device for regular listening and another for games, I'm pretty sure that I'd have to go menu diving to switch between the two.  

Assuming this set up functions as I imagine it, I'd probably go with something like an Audio gd NFB-12, but I realized that I think I'm getting a bit ahead of myself.  This seems to be an unusual set up (X-Fi > DAC > Headphone) for accomplishing this and I realized that I don't know whether or not the X-Fi can still do CMSS headphone or whatnot over optical.  Does anyone know is this will work?  

Even over USB?  That sounds odd to me, considering that Windows would see the USB DAC as a separate audio device, it doesn't seem as though the X-Fi would be able to do anything to the audio being received by the USB device.  

I'm also curious what a set up like this would be to live with - Is it complicated to switch between the resulting headphone setup and the stereo out on my card for speakers?  

Update: I'm getting pretty tired of my X-Fi and its many ways of not working.  Getting stuck in one mode or another, freezing up the whole computer if I change a setting at the wrong time, sometimes having a noise floor for no reason, those kinds of things.  

How complex is it to switch between a gaming optimized and music optimized set up on the Xonar STX?  I'd lose Alchemy, but I only have one game that needs it, and EAX HD, but that's old news and barely any games used it.  Would I lose anything else?  I'd probably just run line out from the STX to an amp.  My X-Fi seems to be behaving right now, so it may yet remain in my system.  

The STX has Dolby headphone, which may or may not be better for me.  Or is this something to do with in game stuff?  I haven't tried it yet.  Does the Titanium HD have a true line out?  

And is it bad for sound quality to use my case's front panel connector?  

I only use the virtual business for playing games.  I need to give dolby headphone a proper try.