Even then, the signal-to-noise ratios of onboard has been good enough for years now. Sure, you might notice a slight difference with a good pair of headphones, but in practice, not so much.
My previous computer was a Q6600 with a SoundBlaster. The sound card did have better sound than the integration audio. For the most part it sounded okay, but the onboard did have a small buzz which was noticeable at higher volumes. It also did not support as many channels, so a small amount of the time some sounds in games would cut out. The SoundBlaster card did not have any buzz, supported more channels, and generally sounded slightly better. But I admit the difference was minor.
When I put together my Ivy Bridge i7 system a year and a half ago, I again compared the state of a (then) brand new integrated chip (RealTek something or other) with the SoundBlaster. No difference. No buzzing either way, and the integrated sound supports plenty of channels. So I agree, but some people in this thread have mentioned the time was 10-15 years ago when I think it is half that long. Regardless of how we got to this point, this is where we are at now.