A wall wart is a transformer that you stick in the power socket to get power you need for your equipment. They create magnetic fields around them, which interferes with A/D and D/A converters. However, the converters on the 8/24 are on the PCI card and thus pretty safe from the transformer. However, again, they're subject to the even worse magnetic fields produced by the rest of the computer so that's not a good thing either. Having the wall wart in the breakout box or actually on the wall is "six or half a dozen" when the converters are in the computer.
I think the 8/24 is a great card and probably hard to beat at $275. I think it costed about $800 in Sweden. It was my choice before I stumbeled across the c-port, which was claimed to be better performance and a lot cheaper. I cannot confirm the better performance though. I read a few review about the c-port, all good, but it's always up to your ears.
Why don't they just make one soundcard so we didn't have to choose?
/Ola