The Elder Scrolls and Fallout, huh?
Arena and Daggerfall are DOS games, so they wouldn't benefit. Morrowind uses DirectSound3D; no mentions of EAX, but you should get the positional audio advantage. Oblivion has an ALchemy entry, suggesting it uses DirectSound3D, but I can't say for sure or not if that actually is the case. Skyrim has purely software-driven audio.
Fallout 1 and 2 are isometric-perspective games that wouldn't benefit anyway. I'm not sure about Fallout 3 and New Vegas; even though I do own them, I haven't even played either one yet simply because I keep putting Fallout 2 off for some reason. Still, I could fire them up and test them out a bit to make sure, since I have a knack for this sort of thing. (It's incredibly obvious to my ears whether CMSS-3D Headphone is getting proper 3DPA data or 7.1 channels.)
I do have to warn you that all these binaural surround technologies will probably result in a slight hit to sound quality in exchange for the positional benefits. Whether you'll find that acceptable or not is something only you can decide. The only one that might negate any sound quality hit is the Smyth Realiser, given the hype-filled reactions and that $3,000+ price tag, and that ultimately will depend on what speaker system and room you can make a recording in.
If it's really slamming/impactful bass you want for those explosions, though, I don't think any headphone will really deliver compared to a full-range speaker or a subwoofer. I've thought about adding a subwoofer to my headphone setup precisely to get around this, but I just don't have the money for it right now. (Good subwoofers that can go all the way down to 20 Hz and not sound like "one-note bass" probably aren't cheap by any means.)
For a home theater surround sound system with an external receiver, the sound card is just a DSP at that point because the DAC that's actually doing the work is in the receiver. Do note that for S/PDIF, you'll need to enable Dolby Digital Live or DTS Connect to actually get the surround channels to the receiver. Only a select few sound cards have HDMI, those being the Auzentech X-Fi HomeTheater HD and Asus Xonar HDAV, all of which I recall being stuck on the slightly outdated HDMI 1.3 standard (we're on HDMI 1.4 now). You could let the graphics card handle HDMI audio...if you don't mind losing hardware-accelerated DirectSound3D and OpenAL support (along with EAX) in the process.
As for X-Fi drivers, Creative does not have the best track record, to say the least. I must be lucky, because over the past few years, my cards (X-Fi Prelude, X-Fi Forte, X-Fi HomeTheater HD) have worked in Windows 7 64-bit generally without complaint. The Titanium HD in particular has a very solid driver base, with less quirks in the time I've had it compared to the Auzentech cards (which still use Creative's drivers).
However, I should point out that it's not like other brands of sound devices don't have issues. I've read complaints about Xonar cards (specifically sudden loud ear-popping noises). I've read complaints about Realtek integrated audio codecs. Seems like anyone who owns a sound device is going to have problems with it somewhere along the line due to drivers, no matter the brand. About the only one I haven't heard complaints about is HT Omega, and that's just because nobody seems to buy or talk about their cards. Any time someone goes shopping for a C-Media chipset card, it's always Asus and not HT Omega for some reason, perhaps because HT Omega offers almost no PCI-Express cards while Asus has several. (The entire Claro Halo line is PCI-only, and slightly more expensive than the Essence ST(X).)
For Windows 8 support, it looks like Creative's released some "beta" drivers that might install and work. I haven't tested them myself simply because I really don't like the UI direction Microsoft is taking with Windows 8. Still, I wouldn't worry too much about Windows 8 driver support once it releases, since it's not like there's a major sound stack change like the XP-to-Vista transition and it looks like Creative will properly support their hardware under the new OS.
X-Fi cards are not known for having proper headphone amplifiers built-in. With something like a Xonar Essence STX or the HT Omega Claro Halo, it's like having a FiiO E9 built-in at less extra cost than buying the Titanium HD and an E9. Since most people opt for more demanding dynamic/ortho headphones when starting out their Head-Fi journey and aren't as insistent on gaming DSP features as I am, they find the C-Media cards the more cost-effective buy.
However, if you're going to buy an external amp anyway, suddenly the Titanium HD becomes the more cost-effective card since you're not paying for headphone amp circuitry you're not using. This works out pretty well for me since my Stax SR-Lambda, like all electrostatics, cannot be driven by conventional amplifiers directly, and all of my dynamic headphones are sensitive enough to work out of anything unamped. It also makes matching the amp to the headphones that much easier, whereas people with good amps in their sound cards might instead try to match the headphones to their amp and limit their options.
As for a final sound card recommendation, because you want to set up a surround speaker system, I can only recommend the Titanium HD or any other two-analog-channel card if you're planning to connect the surround speaker system via S/PDIF to a receiver and switching between it and headphones by turning Dolby Digital Live or DTS Connect on or off. (The X-Fi control panel will automatically switch to 5.1 when you turn it on, and back to the last speaker mode when you turn it off, making it easy.
Hope this helps, even if it's a lot of text to read.