Summing up on multiple issues from one question:
I've been doing some video-editing using a pinnacle DC10+ which doesn't have any sound related hardware, you have to use your PC's general sound hardware. I'n the DC10+ forums it got generally known that the SB Live drivers were PCI bandwith hogs claiming a certain amount of bandwith on the PCI channel despite low load on the soundcard itself, thus causing dropped frames, since video requires high bandwidth. I don't have any first hand experience but got the impression that audigy(2) drivers behave same way.
Regarding M-Audio's claims: An audiophile (a colleague of mine) uses a SB Audigy for gaming purposes, but whenever its music or DVD movie playback he uses an M-Audio Delta 44 for sound quality. He uses SB Audigy due to EAX hardware acceleration, for hardcore gamers SB Áudigy cards are no doubt the best.
I haven't experienced a SB Audigy2 but believe sound quality to very good. I have just today received an M-Adio Revolution 7.1and all I can say is that I'm thrilled, my speakers (and headphones) have never sounded better (that is with CD's, MP3 format now show some severe drawbacks due to the destructive compression - especially drums, but that is MP3 shortcomings).