If you check out the link provided by Audioengr, above, you'll find four current USB converters and a pretty clear review of the results. There's only one I know of that I would want to add, and that's the Blue Circle Thingy (which will also function as a DAC while you save for your dream outboard converter).
Briefly, yes the results are decent and can be very good indeed.
Briefly, yes the results are decent and can be very good indeed.