Hi Jaramill,
in response to actual concerns.
You will not lose positional audio by modding. What you might lose is being able to hear the footsteps at all because of the increased bass of other in game (environmental) noises.
All audio cards comply with the 20mw output so amps can accept them without distortion. (some do 30 though, but they are not strictly compliant, they assume headphones, many only do 10mw to be well within compliance.)
As above, then you may need an amp if you want louder.
Your choice of Creative Labs Soundblaster X-Fi Titanium card should give very clear, loud and precise audio without the need of an amp if gaming is what you want.
Bass mod is *required for music, and and amp if you really want that to blow your head off!
An amp will always make it louder if that is needed, all good quality cards (like yours) expect an amp, not headphones.
If what you say is correct, then you have the perfect audio already, as designed by one of the finest. This mod thread is about putting the oommph in, but then you will be making a trade off.
Warm Regards
I