As far as sound quality goes, external cards will always be best but the Asus DG is a very good card for the money, I still have one in my upstairs PC. I'd personally spend the bit extra and get a Z card but thats just me and only selfish reasons of not liking asus's sound card team and not that the DG is a bad card.
Would external card like u7 or x-fi usb, work passively powered by other sources than pc too ? I could use it as amp for my 360 or jsut as a simple receiver that helps me keep connected all my devices to one box.
That would be more than just a pc sound card and It would totally jsutify spending more money. But if externals are only for pc, then I dont see a point- better take xonar dg or sbz and be done with it.
if anyone knows what I am asking for x-fi usb, please answer. it looks like perfect device for me if it can work by drawing power also from otehr sources than pc. (work at least as amp. I could understand that dac part of it could require drivers and work only with pc)