Better positional audio cues go to all output formats, not just stereo. And you should definitely think on modding proper headphones to have a mic on them, as virtually all headsets (with a few rare exceptions) are borderline awful, stereo and "5.1" headsets alike.
Being able to locate sound sources despite it's location (width, height and obstructions taken in account) is something that's far improved on (hardware) OpenAL vs regular renderers, just like being able to get a dimensional perception of environments (which isn't the same as environmental effects). The X-Fi DSP then takes over and enhances things based on the supplied data, which is 2 steps further where other solutions are, namely the lack of a dedicated DSP and hardware support for OpenAL.
With dirt cheap renderers like XAudio and non-hybrid versions of FMOD, audio is very much unimpressive due to forced downmixing and, like NamelessPFG, geared towards low end/budget/cheap hardware. Luckily, many games come with alternate renderer options or post launch patches.
About taking graphics over realistic sound, well... that's where we agree to disagree. Perfect or near perfect audio gives me a very faithful visual representation of my entire surroundings. What people should realize is that spending $1000 on video and $5 (the average onboard audio chip price) on audio is going to make up for a very unbalanced system. With $900, the user will still get smashingly impressive graphics, while $100 makes for a difference that's very close to night and day.