Well, this is discussed in this thread:
http://www.chiefdelphi.com/forums/sh...rial+adapte r
(I'm a little embarrassed after reading this thread; the thread creator is none other than the programmer I worked with on T3 last year...

)
I have noticed that it isn't the hardware that matters so much as the driver that comes with it. It's really a shot in the dark.
Ensure there is a good return policy on the one you're going to buy, and go for it. Try it out. Return it if it doesn't work.
I would tell you what I've got, but I am not even sure, there is no brand name or model number anywhere on either of my converters.
Good luck...
JBot