I have the Alesis Multimix 8USB and I don't recommend it. Too many glitches in the audio using the USB Audio interface. The Alesis manual says if you get glitches then it is probably your chipset.. well I was using an older ASUS motherboard with AMD and Via chipset and I read its USB chipset had problems. I bought a brand new P4 LGA775 2.6ghz processor alogn with MSI 915 Intel chipset motherboard. Although it works a bit better now, I still get those random glitches in the audio. So now I end up just using the board as a preamp only and have its output go to my Soundblaster Audigy PCI card.
I'd recommend getting the M-Audio DMP3 dual mic pre for $150 over the alesis. And then use some good sound card or external A/D converter like the M-Audio Delta 1010. I am gonna go with the M-Audio DMP3 or M-Audio Tampa as soon as I get some money and sell this Alesis. I guess I'll get the Delta 1010 as well, if the audigy's A/D converters aren't good enough. I don't have any real noise coming from the Audigy that I can tell though.
James