I would have probably went for the HD if I knew I was just going to get an external amp anyways.
HP out to RCA seems to work fine for me though now that I've got the ground loop fixed; I can't really tell any difference in quality. But after hearing Creative has better gaming support and all that, kinda wish I would have went that route.
I still use it on very high gain with 100% volume even though the buzzing is gone. It seems to have the same volume as RCA to RCA that way, and to me when I have to turn up the volume knob less to get a higher volume it makes it seem like quality is better(which I'm sure is purely a psychological thing).