Hi Don, I have limited experience of M-Audio Black Box USB
from about 5 years ago, and though primarily a guitar FX/amp emulator,
it was a good enough audio interface for most solo recording demo purposes.

E-MU were, maybe still are, considered to be the better pro standard 'economy' interfaces
because of the higher quality A/D converters used, which if I remember correctly were comparable
to Pro Tools hardware converters.
Plus, they include very comprehensive software bundles.

here's their latest USB product range:

http://www.emu.com/products/welcome.asp?category=610

Then there are the Line 6 USB range of price concious [entry level to Pro studio] interfaces, which are serious contenders,
notable for very flexible recording input/output configurations and highly 'authentic' software amp/speaker/mic-preamp/FX emulations.


Plenty of serious value for money gear to choose from these and other popular brands.