[Wayne DePrince Jr.]
however, as i mentioned, some of these interfaces i am
also
testing out (e.g. Edirol FA-66, Zoom U-44) have a Hi-Z button on an input
which supposedly allows direct inputing of a passive signal.
High-quality DI employs an audio transformer, a relatively large and
heavy item. It's very unlikely you'll find one in a general-purpose
audio interface built to sell in numbers.
To connect an electric guitar via USB, I'd choose an interface that
supplies phantom power and an active DI box. Many people seem to be
happy with simpler solutions though.
Cheers, Tim