CMSS-3D Headphone makes it all worth it if you ask me. Just make sure the Windows sound control panel is set to 7.1 speakers while the X-Fi drivers themselves are set to Headphones. This is needed to enable CMSS-3D Headphone and not one of the other similarly-named technologies. (I don't have a Titanium HD myself to confirm that, but word is that the Titanium HD provides 5.1 at the very least because it also has S/PDIF-out, which would work with Dolby Digital Live or DTS Connect. Not that you're even going to be using either of those...)
US$180 worth it, though? No way, you can get a Titanium HD for under US$130 easily, possibly even less. Put some of that savings toward better headphones if you must. Some may argue that if you're only going to be gaming, no music listening or anything of the sort, you could get by with a cheaper X-Fi Titanium at US$65 or so.
While HRTF filters are inherently your-mileage-may-vary (everyone has a differently sized and shaped head, thus a different HRTF), the generic one used by the likes of CMSS-3D Headphone works excellently for me. So much, in fact, that I don't even feel the need to bother with speakers because the imaging might actually be worse (to say nothing of the setup hassles and extra cost).
