"I've used a SBLive in Linux, and had low latency audio working perfectly well."
Yea, after you did what, install the kX driverset which comes with an ASIO driver? (I helped design that.)
"You still do not understand what ALSA or ASIO are."
Given the statement directly above, you might wish to think again on that.
"ALSA can give as low a latency as the hardware is capable of."
Since when? I'm still getting 1/4 second latency using ALSA trying to play Wolf:ET. That's just on playback.
"ALSA is the lowest level of the sound stack, so talking to it directly gives the lowest latency. Pulseaudio runs on top of ALSA, as do all sound servers on Linux."
I see you've never heard of OSS. It sure as fuck doesn't talk to ALSA at all.
"Most likely, you were using direct analog passthrough within the sound card in XP, and software monitoring in Linux. Both paths are also possible in ALSA on Linux."
Nope. SBLive does not have a direct analog pass-through (at least this revision, with the additional DRM restricting the 'What U Hear' option) This is simply testable across several OSes - XP/2K give no lag. Vista and 7 introduce about ~150ms lag. OSS gets me ~20ms latency. ALSA gets me ~50. Pulseaudio can't even handle it and clips the fuck out of my line-in.
"I am a professional audio engineer with 25 years of experience, so these things do matter to me."
I can't tell. Bet you're the type that compressor-limits the fuck out of everything, too.