I've had this problem ever since i've used sabayon. Basically, I went through a string of computers that had sound cards that weren't always up to date in support by linux. ALSA drivers did not work, and I was left waiting for months till something reached alsa-9999. Anyhow, I always found it a real pain because alsa was built into the kernel, and I had to rebuild the kernel just to disable built in alsa, so that I could "emerge alsa-9999". Now some of you may say "Whats the big deal". Well, its more an issue of lack of consistency. I can "emerge nvidia-driver" to my hearts content as soon as I finish installing, but I cannot "emerge alsa", it gives you warnings about it existing in kernel already.
All in all, i'd hate for someone not to use sabayon just because they couldn't emerge alsa to their latest audio drivers in the future.
Yes yes, I know this is extremely minor, but had I not known how to recompile my kernel, I would have likely never chosen sabayon linux.